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TLS CVE-2025-49812

| EUVDEUVD-2025-21016 HIGH
Improper Authentication (CWE-287)
2025-07-10 security@apache.org
Apache TLS Session Fixation Http Server Red Hat Suse Apache HTTP Server
7.4
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
7.4 HIGH
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Ubuntu
MEDIUM
qualitative
SUSE
HIGH
qualitative
Red Hat
7.5 MEDIUM
qualitative

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

Lifecycle Timeline

4
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
EUVD ID Assigned
Mar 16, 2026 - 06:52 euvd
EUVD-2025-21016
Analysis Generated
Mar 16, 2026 - 06:52 vuln.today
CVE Published
Jul 10, 2025 - 17:15 nvd
HIGH 7.4

DescriptionCVE.org

In some mod_ssl configurations on Apache HTTP Server versions through to 2.4.63, an HTTP desynchronisation attack allows a man-in-the-middle attacker to hijack an HTTP session via a TLS upgrade.

Only configurations using "SSLEngine optional" to enable TLS upgrades are affected. Users are recommended to upgrade to version 2.4.64, which removes support for TLS upgrade.

AnalysisAI

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.

Technical ContextAI

The vulnerability exploits HTTP Upgrade mechanism (RFC 7230) combined with STARTTLS-like TLS upgrade functionality in mod_ssl. When 'SSLEngine optional' is configured, Apache allows clients to negotiate TLS upgrades mid-connection via HTTP Upgrade headers and 101 Switching Protocols responses. The root cause is CWE-287 (Improper Authentication) manifested as a desynchronization between how the proxy/server interprets request boundaries during the upgrade handshake. An attacker positioned as a MITM can send crafted HTTP requests that cause the server and client to disagree on where one request ends and another begins, allowing the attacker to inject commands into an established TLS session. This is a variant of HTTP request smuggling (CWE-444) at the TLS upgrade layer. Affected CPE: cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:* (versions up to 2.4.63 with mod_ssl and SSLEngine optional configuration).

RemediationAI

  • priority: CRITICAL; action: Upgrade to Apache HTTP Server 2.4.64 or later; rationale: Version 2.4.64 removes TLS upgrade support entirely, eliminating the attack surface. This is the vendor-recommended fix.
  • priority: HIGH; action: If upgrade is not immediately possible, remove or disable 'SSLEngine optional' configuration; rationale: Change SSLEngine directive from 'optional' to 'on' (require TLS) or 'off' to disable SSL/TLS entirely for affected virtual hosts. This prevents the upgrade mechanism that enables the attack.; config_example: Change: SSLEngine optional | To: SSLEngine on
  • priority: HIGH; action: Disable HTTP-to-HTTPS upgrade mechanisms; rationale: Remove or comment out HTTP Upgrade header handling and 101 Switching Protocols support if possible through mod_ssl configuration.
  • priority: MEDIUM; action: Implement MITM detection and network segmentation; rationale: Deploy certificate pinning on clients, use VPNs, and enforce internal TLS for server-to-server communication to reduce MITM risk while patching.

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Vendor StatusVendor

Ubuntu

Priority: Medium
apache2
Release Status Version
trusty needs-triage -
xenial released 2.4.18-2ubuntu3.17+esm16
upstream released 2.4.64-1
bionic released 2.4.29-1ubuntu4.27+esm6
focal released 2.4.41-4ubuntu3.23+esm2
jammy released 2.4.52-1ubuntu4.15
noble released 2.4.58-1ubuntu8.7
plucky released 2.4.63-1ubuntu1.1
questing released 2.4.64-1ubuntu1
USN-7639-1 USN-7639-2

Debian

apache2
Release Status Fixed Version Urgency
bullseye fixed 2.4.65-1~deb11u1 -
bullseye (security) fixed 2.4.66-1~deb11u1 -
bookworm fixed 2.4.65-1~deb12u1 -
bookworm (security) vulnerable 2.4.62-1~deb12u2 -
trixie fixed 2.4.66-1~deb13u2 -
forky, sid fixed 2.4.66-8 -
(unstable) fixed 2.4.64-1 -
DLA-4270-1

SUSE

Severity: High
Product Status
Container suse/manager/4.3/proxy-httpd:4.3.16.9.67.10 Image SLES15-SP4-Manager-Proxy-4-3-BYOS Image SLES15-SP4-Manager-Proxy-4-3-BYOS-Azure Image SLES15-SP4-Manager-Proxy-4-3-BYOS-EC2 Image SLES15-SP4-Manager-Proxy-4-3-BYOS-GCE Image SLES15-SP4-Manager-Server-4-3-BYOS Image SLES15-SP4-Manager-Server-4-3-BYOS-Azure Image SLES15-SP4-Manager-Server-4-3-BYOS-EC2 Image SLES15-SP4-Manager-Server-4-3-BYOS-GCE Image SLES15-SP4-SAP Image SLES15-SP4-SAP-Azure Image SLES15-SP4-SAP-EC2 Image SLES15-SP4-SAP-GCE Image SLES15-SP4-SAPCAL Image SLES15-SP4-SAPCAL-Azure Image SLES15-SP4-SAPCAL-EC2 Image SLES15-SP4-SAPCAL-GCE Image SLES15-SP5-SAPCAL-Azure Image SLES15-SP5-SAPCAL-EC2 Image SLES15-SP5-SAPCAL-GCE Affected
Container suse/manager/5.0/x86_64/proxy-httpd:5.0.5.1.7.26.2 Container suse/manager/5.0/x86_64/server:5.0.5.1.7.33.2 Image SLES15-SP6-SAP Image SLES15-SP6-SAP-Azure Image SLES15-SP6-SAP-EC2 Image SLES15-SP6-SAP-GCE Image SLES15-SP6-SAPCAL Image SLES15-SP6-SAPCAL-Azure Image SLES15-SP6-SAPCAL-EC2 Image SLES15-SP6-SAPCAL-GCE Affected
Container suse/multi-linux-manager/5.1/x86_64/proxy-httpd:5.1.1.8.9.2 Container suse/multi-linux-manager/5.1/x86_64/proxy-salt-broker:5.1.2.9.13.2 Container suse/multi-linux-manager/5.1/x86_64/server:5.1.1.8.7.1 Image SLES15-SP7-SAPCAL-Azure Image SLES15-SP7-SAPCAL-EC2 Image SLES15-SP7-SAPCAL-GCE Image proxy-httpd-image Image server-image Affected
SUSE Enterprise Storage 7.1 Fixed
SUSE Liberty Linux 7 LTSS Fixed

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CVE-2025-49812 vulnerability details – vuln.today
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