Apache HTTP Server

Uncontrolled resource consumption in Apache HTTP Server's mod_md module allows remote unauthenticated attackers to exhaust server resources via malformed OCSP response data, affecting versions 2.4.30 through 2.4.66. The vulnerability enables attackers to achieve confidentiality, integrity, and availability impacts with low complexity exploitation over the network. No active exploitation confirmed (not in CISA KEV), but the network-accessible attack surface and lack of authentication requirement make this a credible threat requiring prompt patching to version 2.4.67.

Remote attackers can crash Apache HTTP Server 2.4.66 and earlier by sending malicious requests that trigger a NULL pointer dereference in mod_dav_lock, causing denial of service. The vulnerability affects only servers with mod_dav_lock enabled, a legacy module whose primary use-case (Apache Subversion < 1.2.0) is obsolete in modern deployments. CISA SSVC indicates no active exploitation, but the attack is automatable against susceptible configurations. CVSS 7.5 (High) reflects network-accessible, unauthenticated denial of service, though real-world impact is limited to the small subset of servers still running mod_dav_lock.

Timing attack against mod_auth_digest in Apache HTTP Server 2.4.66 allows remote unauthenticated attackers to bypass Digest authentication with high attack complexity. The vulnerability exploits measurable timing differences in digest credential validation, enabling credential compromise without valid authentication. Apache has released patched version 2.4.67; no active exploitation has been confirmed, but CISA SSVC framework indicates automatable exploitation is not feasible due to the timing attack's sensitivity requirements.

Null pointer dereference in mod_authn_socache in Apache HTTP Server 2.4.66 and earlier allows unauthenticated remote attackers to crash child processes in caching forward proxy configurations, resulting in denial of service. The vulnerability has CVSS 5.3 (medium) with network accessibility and no authentication required, but is limited to partial availability impact affecting only specific proxy deployments. Vendor-released patch: version 2.4.67.

HTTP response splitting in Apache HTTP Server 2.4.0 through 2.4.66 allows remote attackers to inject arbitrary HTTP headers and content when the server acts as a proxy to untrusted or compromised backend servers, enabling cache poisoning, session fixation, and cross-site scripting attacks. CVSS 6.5 (moderate) with network attack vector, no authentication required, and confirmed automatable exploitation per CISA SSVC framework. Vendor-released patch: version 2.4.67.

Out-of-bounds read in mod_proxy_ajp of Apache HTTP Server through version 2.4.66 allows remote unauthenticated attackers to disclose sensitive information via a crafted AJP protocol request. The vulnerability has a CVSS score of 5.3 (moderate) with no active exploitation confirmed. Upgrade to version 2.4.67 to remediate.

Improper null termination and out-of-bounds read vulnerability in Apache HTTP Server through version 2.4.66 allows remote unauthenticated attackers to trigger information disclosure with low complexity exploitation. The vulnerability has a CVSS score of 5.3 (medium) with network-accessible attack vector and no user interaction required, though technical impact is limited to confidentiality (partial information disclosure). Vendor-released patch: version 2.4.67 addresses the issue.

Buffer over-read in Apache HTTP Server through 2.4.66 enables remote unauthenticated information disclosure at network scale. Attackers can read sensitive memory content without authentication or user interaction, achieving high confidentiality impact with low attack complexity. EPSS exploitation probability and KEV status not provided, but SSVC framework confirms the vulnerability is automatable with partial technical impact and no active exploitation detected at time of analysis. Patch released in version 2.4.67.

Local .htaccess authors can escalate privileges to read arbitrary files as the httpd daemon user in Apache HTTP Server 2.4.66 and earlier. The vulnerability requires low-privilege authenticated access to create or modify .htaccess files, but exploits misconfigured module interactions to bypass intended access controls. Apache has released version 2.4.67 to address this issue. SSVC assessment indicates no active exploitation and non-automatable attack vector, with EPSS data not yet available for this recent disclosure.

CVE-2025-58098 is a security vulnerability (CVSS 8.3). High severity vulnerability requiring prompt remediation.

A security vulnerability in Apache HTTP Server (CVSS 5.4). Remediation should follow standard vulnerability management procedures.

A security vulnerability in Apache HTTP Server (CVSS 6.5). Remediation should follow standard vulnerability management procedures.

Server-Side Request Forgery (SSRF) vulnerability  in Apache HTTP Server on Windows with AllowEncodedSlashes On and MergeSlashes Off  allows to potentially leak NTLM hashes to a malicious server via SSRF and malicious requests or content Users are recommended to upgrade to version 2.4.66, which fixes the issue.

An integer overflow in the case of failed ACME certificate renewal leads, after a number of failures (~30 days in default configurations), to the backoff timer becoming 0. Attempts to renew the certificate then are repeated without delays until it succeeds. This issue affects Apache HTTP Server: from 2.4.30 before 2.4.66. Users are recommended to upgrade to version 2.4.66, which fixes the issue.

CVE-2025-53020 is a late release of memory after effective lifetime vulnerability (use-after-free) in Apache HTTP Server versions 2.4.17 through 2.4.63 that allows unauthenticated remote attackers to cause denial of service with high availability impact. The vulnerability has a CVSS score of 7.5 (high severity) with network-accessible attack vector and low attack complexity, making it easily exploitable without authentication. Affected organizations running vulnerable Apache HTTP Server versions should prioritize upgrading to version 2.4.64 immediately.

CVE-2025-49812 is an HTTP request smuggling/desynchronization vulnerability in Apache HTTP Server's mod_ssl that allows man-in-the-middle attackers to hijack HTTPS sessions by exploiting improper handling of TLS upgrades. Only Apache HTTP Server versions through 2.4.63 with 'SSLEngine optional' configurations are affected, enabling session hijacking with high confidentiality and integrity impact. The vulnerability requires network-level access and careful timing but does not require user interaction or privileges; upgrade to 2.4.64 (which removes TLS upgrade support entirely) is the recommended mitigation.

CVE-2025-49630 is a denial of service vulnerability in Apache HTTP Server versions 2.4.26 through 2.4.63 that can be triggered by untrusted remote clients when a reverse proxy is configured with HTTP/2 backend support and ProxyPreserveHost enabled, causing an assertion failure that crashes the proxy process. The vulnerability has a CVSS score of 7.5 (High) with network-accessible attack vector and no authentication required, making it immediately exploitable by unauthenticated remote attackers.

CVE-2025-23048 is an authentication bypass vulnerability in Apache HTTP Server 2.4.35-2.4.63 affecting mod_ssl configurations with multiple virtual hosts using different client certificate restrictions. An attacker with valid client certificates trusted by one virtual host can exploit TLS 1.3 session resumption to access another restricted virtual host if SSLStrictSNIVHostCheck is not enabled, achieving unauthorized access to confidential information and potentially modifying data. This is a network-accessible vulnerability with no authentication required and high real-world impact.

CVE-2024-47252 is a security vulnerability (CVSS 7.5). High severity vulnerability requiring prompt remediation.

CVE-2024-43394 is a Server-Side Request Forgery (SSRF) vulnerability in Apache HTTP Server on Windows (versions 2.4.0-2.4.63) that allows unauthenticated remote attackers to leak NTLM credential hashes to malicious servers through unvalidated request input processed by mod_rewrite or Apache expressions. The vulnerability exploits Windows SMB/UNC path handling to trigger NTLM authentication, potentially compromising domain credentials. This is a high-severity issue affecting all default Windows installations without explicit UNC path filtering.

CVE-2024-43204 is a Server-Side Request Forgery (SSRF) vulnerability in Apache HTTP Server when mod_proxy is loaded, allowing unauthenticated attackers to initiate outbound proxy requests to attacker-controlled URLs. The vulnerability requires an uncommon configuration where mod_headers is used to modify Content-Type headers based on user-supplied HTTP request values. Apache recommends immediate upgrade to version 2.4.64 to remediate this high-integrity-impact issue.

HTTP response splitting vulnerability in Apache HTTP Server core allows network-based attackers without authentication to inject arbitrary HTTP headers and content into responses by manipulating Content-Type headers in proxied or hosted applications, potentially enabling cache poisoning, session hijacking, or XSS attacks. Affects Apache HTTP Server versions prior to 2.4.64, with a critical note that the initial patch in 2.4.59 was incomplete. This is a regression/incomplete fix of CVE-2023-38709, indicating patch evasion and suggesting active exploitation interest.

Apache httpd allows remote attackers to read secret data from process memory if the Limit directive can be set in a user's .htaccess file, or if httpd.conf has certain misconfigurations, aka. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and EPSS exploitation probability 93.8%.

Apache HTTP Server, in all releases prior to 2.2.32 and 2.4.25, was liberal in the whitespace accepted from requests and sent in response lines and headers. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.

In Apache HTTP Server versions 2.4.0 to 2.4.23, malicious input to mod_auth_digest can cause the server to crash, and each instance continues to crash even for subsequently valid requests. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 33.2% and no vendor patch available.

In Apache HTTP Server versions 2.4.0 to 2.4.23, mod_session_crypto was encrypting its data/cookie using the configured ciphers with possibly either CBC or ECB modes of operation (AES256-CBC by. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and EPSS exploitation probability 41.7%.

A maliciously constructed HTTP/2 request could cause mod_http2 in Apache HTTP Server 2.4.24, 2.4.25 to dereference a NULL pointer and crash the server process. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 38.4% and no vendor patch available.

When under stress, closing many connections, the HTTP/2 handling code in Apache httpd 2.4.26 would sometimes access memory after it has been freed, resulting in potentially erratic behaviour. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

In Apache httpd before 2.2.34 and 2.4.x before 2.4.27, the value placeholder in [Proxy-]Authorization headers of type 'Digest' was not initialized or reset before or between successive key=value. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 49.5%.

In Apache httpd 2.2.x before 2.2.33 and 2.4.x before 2.4.26, mod_mime can read one byte past the end of a buffer when sending a malicious Content-Type response header. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and EPSS exploitation probability 30.1%.

The HTTP strict parsing changes added in Apache httpd 2.2.32 and 2.4.24 introduced a bug in token list parsing, which allows ap_find_token() to search past the end of its input string. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 62.8%.

In Apache httpd 2.2.x before 2.2.33 and 2.4.x before 2.4.26, mod_ssl may dereference a NULL pointer when third-party modules call ap_hook_process_connection() during an HTTP request to an HTTPS port. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and EPSS exploitation probability 30.8%.

In Apache httpd 2.2.x before 2.2.33 and 2.4.x before 2.4.26, use of the ap_get_basic_auth_pw() by third-party modules outside of the authentication phase may lead to authentication requirements being. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Improper Authentication vulnerability could allow attackers to bypass authentication mechanisms to gain unauthorized access.

The mod_http2 module in the Apache HTTP Server 2.4.17 through 2.4.23, when the Protocols configuration includes h2 or h2c, does not restrict request-header length, which allows remote attackers to. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and EPSS exploitation probability 68.3%.

The Apache HTTP Server through 2.4.23 follows RFC 3875 section 4.1.18 and therefore does not protect applications from the presence of untrusted client data in the HTTP_PROXY environment variable,. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. Epss exploitation probability 60.3%.

The Apache HTTP Server 2.4.18 through 2.4.20, when mod_http2 and mod_ssl are enabled, does not properly recognize the "SSLVerifyClient require" directive for HTTP/2 request authorization, which. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 17.4%.

The Apache HTTP Server 2.4.17 and 2.4.18, when mod_http2 is enabled, does not limit the number of simultaneous stream workers for a single HTTP/2 connection, which allows remote attackers to cause a. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. Epss exploitation probability 41.5%.

The ap_some_auth_required function in server/request.c in the Apache HTTP Server 2.4.x before 2.4.14 does not consider that a Require directive may be associated with an authorization setting rather. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable. No vendor patch available.

The chunked transfer coding implementation in the Apache HTTP Server before 2.4.14 does not properly parse chunk headers, which allows remote attackers to conduct HTTP request smuggling attacks via a. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. Epss exploitation probability 28.3%.

The read_request_line function in server/protocol.c in the Apache HTTP Server 2.4.12 does not initialize the protocol structure member, which allows remote attackers to cause a denial of service. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. Epss exploitation probability 10.6% and no vendor patch available.

The lua_websocket_read function in lua_request.c in the mod_lua module in the Apache HTTP Server through 2.4.12 allows remote attackers to cause a denial of service (child-process crash) by sending a. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. Epss exploitation probability 18.7% and no vendor patch available.

mod_lua.c in the mod_lua module in the Apache HTTP Server 2.3.x and 2.4.x through 2.4.10 does not support an httpd configuration in which the same Lua authorization provider is used with different. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable. Epss exploitation probability 11.7%.

The handle_headers function in mod_proxy_fcgi.c in the mod_proxy_fcgi module in the Apache HTTP Server 2.4.10 allows remote FastCGI servers to cause a denial of service (buffer over-read and daemon. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. Epss exploitation probability 41.8% and no vendor patch available.

The cache_merge_headers_out function in modules/cache/cache_util.c in the mod_cache module in the Apache HTTP Server before 2.4.11 allows remote attackers to cause a denial of service (NULL pointer. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. This NULL Pointer Dereference vulnerability could allow attackers to crash the application by dereferencing a null pointer.

Memory leak in the winnt_accept function in server/mpm/winnt/child.c in the WinNT MPM in the Apache HTTP Server 2.4.x before 2.4.10 on Windows, when the default AcceptFilter is enabled, allows remote. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. Epss exploitation probability 35.2%.

The mod_cgid module in the Apache HTTP Server before 2.4.10 does not have a timeout mechanism, which allows remote attackers to cause a denial of service (process hang) via a request to a CGI script. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. Epss exploitation probability 44.2%.

Race condition in the mod_status module in the Apache HTTP Server before 2.4.10 allows remote attackers to cause a denial of service (heap-based buffer overflow), or possibly obtain sensitive. Rated medium severity (CVSS 6.8), this vulnerability is remotely exploitable. Public exploit code available and EPSS exploitation probability 75.4%.

The deflate_in_filter function in mod_deflate.c in the mod_deflate module in the Apache HTTP Server before 2.4.10, when request body decompression is enabled, allows remote attackers to cause a. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable. Epss exploitation probability 41.3%.

The mod_proxy module in the Apache HTTP Server 2.4.x before 2.4.10, when a reverse proxy is enabled, allows remote attackers to cause a denial of service (child-process crash) via a crafted HTTP. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable. Epss exploitation probability 57.0%.

The cache_invalidate function in modules/cache/cache_storage.c in the mod_cache module in the Apache HTTP Server 2.4.6, when a caching forward proxy is enabled, allows remote HTTP servers to cause a. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable. Epss exploitation probability 24.4% and no vendor patch available.

The mod_headers module in the Apache HTTP Server 2.2.22 allows remote attackers to bypass "RequestHeader unset" directives by placing a header in the trailer portion of data sent with chunked. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and EPSS exploitation probability 64.7%.

The log_cookie function in mod_log_config.c in the mod_log_config module in the Apache HTTP Server before 2.4.8 allows remote attackers to cause a denial of service (segmentation fault and daemon. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. Epss exploitation probability 41.0%.

The dav_xml_get_cdata function in main/util.c in the mod_dav module in the Apache HTTP Server before 2.4.8 does not properly remove whitespace characters from CDATA sections, which allows remote. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. Epss exploitation probability 30.2%.

mod_session_dbd.c in the mod_session_dbd module in the Apache HTTP Server before 2.4.5 proceeds with save operations for a session without considering the dirty flag and the requirement for a new. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and EPSS exploitation probability 43.7%.

mod_dav.c in the Apache HTTP Server before 2.2.25 does not properly determine whether DAV is enabled for a URI, which allows remote attackers to cause a denial of service (segmentation fault) via a. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable. Public exploit code available and EPSS exploitation probability 38.6%.

mod_rewrite.c in the mod_rewrite module in the Apache HTTP Server 2.2.x before 2.2.25 writes data to a log file without sanitizing non-printable characters, which might allow remote attackers to. Rated medium severity (CVSS 5.1), this vulnerability is remotely exploitable. Epss exploitation probability 39.6%.

Multiple cross-site scripting (XSS) vulnerabilities in the balancer_handler function in the manager interface in mod_proxy_balancer.c in the mod_proxy_balancer module in the Apache HTTP Server 2.2.x. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable. Epss exploitation probability 28.2% and no vendor patch available.

Multiple cross-site scripting (XSS) vulnerabilities in the Apache HTTP Server 2.2.x before 2.2.24-dev and 2.4.x before 2.4.4 allow remote attackers to inject arbitrary web script or HTML via vectors. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable. Epss exploitation probability 10.3% and no vendor patch available.

The mod_proxy_ajp module in the Apache HTTP Server 2.2.12 through 2.2.21 places a worker node into an error state upon detection of a long request-processing time, which allows remote attackers to. Rated medium severity (CVSS 5.0), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and EPSS exploitation probability 26.0%.

The proxy functionality in (1) mod_proxy_ajp.c in the mod_proxy_ajp module and (2) mod_proxy_http.c in the mod_proxy_http module in the Apache HTTP Server 2.4.x before 2.4.3 does not properly. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable. No vendor patch available.

Multiple cross-site scripting (XSS) vulnerabilities in the make_variant_list function in mod_negotiation.c in the mod_negotiation module in the Apache HTTP Server 2.4.x before 2.4.3, when the. Rated low severity (CVSS 2.6), this vulnerability is remotely exploitable. No vendor patch available.

envvars (aka envvars-std) in the Apache HTTP Server before 2.4.2 places a zero-length directory name in the LD_LIBRARY_PATH, which allows local users to gain privileges via a Trojan horse DSO in the. Rated medium severity (CVSS 6.9).

protocol.c in the Apache HTTP Server 2.2.x through 2.2.21 does not properly restrict header information during construction of Bad Request (aka 400) error documents, which allows remote attackers to. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable. Public exploit code available and EPSS exploitation probability 56.0%.

The log_cookie function in mod_log_config.c in the mod_log_config module in the Apache HTTP Server 2.2.17 through 2.2.21, when a threaded MPM is used, does not properly handle a %{}C format string,. Rated low severity (CVSS 2.6), this vulnerability is remotely exploitable. Epss exploitation probability 33.0%.

scoreboard.c in the Apache HTTP Server 2.2.21 and earlier might allow local users to cause a denial of service (daemon crash during shutdown) or possibly have unspecified other impact by modifying a. Rated medium severity (CVSS 4.6), this vulnerability is low attack complexity. Public exploit code available and no vendor patch available.