Varnish Software
Monthly
HTTP/2 request parsing in Vinyl Cache and Varnish Cache enables backend request desync (HTTP request smuggling), exploitable for cache poisoning, authentication bypass, and information disclosure against affected deployments. Vinyl Cache prior to 9.0.1 and Varnish Cache prior to 9.0.3, plus legacy pre-split Varnish Cache branches spanning versions 6.0.14 through 8.0.1, are confirmed affected across three distinct CPE lineages. Exploitation is gated behind an explicitly non-default configuration - HTTP/2 must be enabled via the +http2 feature parameter - which substantially limits exposure; no public exploit code and no CISA KEV listing have been identified at time of analysis.
Varnish Cache 9.0.0 crashes (denial of service) when a remote client exploits timing between timeout_linger and timeout_idle to trigger HTTP/1 request pipelining that causes a workspace overflow in the refactored HTTP/2 architecture. The vulnerability stems from incomplete code path handling during workspace rollback in the recent non-blocking port, allowing prefetched data to exceed workspace_client boundaries and panic the daemon. Vendor-released patch: version 9.0.1. No public exploit code identified at time of analysis, but the attack requires only network access and careful timing, making real-world exploitation feasible for sophisticated attackers.
Varnish Enterprise before version 6.0.16r12 is vulnerable to a workspace overflow denial of service attack that crashes the daemon through the headerplus.write_req0() VCL function. Unauthenticated remote attackers can craft HTTP requests with excessive header fields to trigger a panic and terminate the Varnish server, particularly impacting deployments using shared VCL through Varnish Controller. CVSS base score of 4.0 reflects low availability impact with high attack complexity, and no public exploit code or confirmed active exploitation has been identified.
Denial of service via workspace overflow in Varnish Cache 9 before 9.0.1 and Varnish Enterprise before 6.0.16r11 allows unauthenticated remote attackers to trigger daemon panic through HTTP/2 session upgrade with specific amounts of prefetched data. The vulnerability exploits improper buffer allocation during HTTP/1 to HTTP/2 transport upgrade, causing workspace exhaustion on subsequent pipelined fetch operations. EPSS score of 4.0 (low-to-medium risk) reflects attack complexity and limited scope (local availability impact only), though no public exploit code or active exploitation has been confirmed.
Varnish Cache before 8.0.1 and Varnish Enterprise before 6.0.16r12 mishandle HTTP/1.1 URLs with a root path (/) in unchecked req.url scenarios, enabling cache poisoning and authentication bypass attacks. Unauthenticated remote attackers can exploit this with moderate complexity to poison cached content or bypass authentication controls affecting downstream clients. No active exploitation has been confirmed, though the vulnerability carries a 5.4 CVSS score reflecting network accessibility and partial impact to confidentiality and integrity.
Varnish Enterprise before 6.0.13r13 allows remote attackers to obtain sensitive information via an out-of-bounds read for range requests on ephemeral MSE4 stevedore objects. Rated medium severity (CVSS 4.0), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
Varnish Cache before 7.6.2 and Varnish Enterprise before 6.0.13r10 allow client-side desync via HTTP/1 requests. Rated medium severity (CVSS 5.4), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
libvmod-digest before 1.0.3, as used in Varnish Enterprise 6.0.x before 6.0.11r5, has an out-of-bounds memory access during base64 decoding, leading to both authentication bypass and information. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Buffer Overflow vulnerability could allow attackers to corrupt memory to execute arbitrary code or crash the application.
An HTTP Request Forgery issue was discovered in Varnish Cache 5.x and 6.x before 6.0.11, 7.x before 7.1.2, and 7.2.x before 7.2.1. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Varnish Cache, with HTTP/2 enabled, allows request smuggling and VCL authorization bypass via a large Content-Length header for a POST request. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This HTTP Request/Response Smuggling vulnerability could allow attackers to manipulate HTTP request interpretation between frontend and backend servers.
An issue was discovered in Varnish Cache before 6.0.6 LTS, 6.1.x and 6.2.x before 6.2.3, and 6.3.x before 6.3.2. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in Varnish Cache before 6.0.4 LTS, and 6.1.x and 6.2.x before 6.2.1. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in Varnish HTTP Cache 4.0.1 through 4.0.4, 4.1.0 through 4.1.7, 5.0.0, and 5.1.0 through 5.1.2. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
HTTP/2 request parsing in Vinyl Cache and Varnish Cache enables backend request desync (HTTP request smuggling), exploitable for cache poisoning, authentication bypass, and information disclosure against affected deployments. Vinyl Cache prior to 9.0.1 and Varnish Cache prior to 9.0.3, plus legacy pre-split Varnish Cache branches spanning versions 6.0.14 through 8.0.1, are confirmed affected across three distinct CPE lineages. Exploitation is gated behind an explicitly non-default configuration - HTTP/2 must be enabled via the +http2 feature parameter - which substantially limits exposure; no public exploit code and no CISA KEV listing have been identified at time of analysis.
Varnish Cache 9.0.0 crashes (denial of service) when a remote client exploits timing between timeout_linger and timeout_idle to trigger HTTP/1 request pipelining that causes a workspace overflow in the refactored HTTP/2 architecture. The vulnerability stems from incomplete code path handling during workspace rollback in the recent non-blocking port, allowing prefetched data to exceed workspace_client boundaries and panic the daemon. Vendor-released patch: version 9.0.1. No public exploit code identified at time of analysis, but the attack requires only network access and careful timing, making real-world exploitation feasible for sophisticated attackers.
Varnish Enterprise before version 6.0.16r12 is vulnerable to a workspace overflow denial of service attack that crashes the daemon through the headerplus.write_req0() VCL function. Unauthenticated remote attackers can craft HTTP requests with excessive header fields to trigger a panic and terminate the Varnish server, particularly impacting deployments using shared VCL through Varnish Controller. CVSS base score of 4.0 reflects low availability impact with high attack complexity, and no public exploit code or confirmed active exploitation has been identified.
Denial of service via workspace overflow in Varnish Cache 9 before 9.0.1 and Varnish Enterprise before 6.0.16r11 allows unauthenticated remote attackers to trigger daemon panic through HTTP/2 session upgrade with specific amounts of prefetched data. The vulnerability exploits improper buffer allocation during HTTP/1 to HTTP/2 transport upgrade, causing workspace exhaustion on subsequent pipelined fetch operations. EPSS score of 4.0 (low-to-medium risk) reflects attack complexity and limited scope (local availability impact only), though no public exploit code or active exploitation has been confirmed.
Varnish Cache before 8.0.1 and Varnish Enterprise before 6.0.16r12 mishandle HTTP/1.1 URLs with a root path (/) in unchecked req.url scenarios, enabling cache poisoning and authentication bypass attacks. Unauthenticated remote attackers can exploit this with moderate complexity to poison cached content or bypass authentication controls affecting downstream clients. No active exploitation has been confirmed, though the vulnerability carries a 5.4 CVSS score reflecting network accessibility and partial impact to confidentiality and integrity.
Varnish Enterprise before 6.0.13r13 allows remote attackers to obtain sensitive information via an out-of-bounds read for range requests on ephemeral MSE4 stevedore objects. Rated medium severity (CVSS 4.0), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
Varnish Cache before 7.6.2 and Varnish Enterprise before 6.0.13r10 allow client-side desync via HTTP/1 requests. Rated medium severity (CVSS 5.4), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
libvmod-digest before 1.0.3, as used in Varnish Enterprise 6.0.x before 6.0.11r5, has an out-of-bounds memory access during base64 decoding, leading to both authentication bypass and information. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Buffer Overflow vulnerability could allow attackers to corrupt memory to execute arbitrary code or crash the application.
An HTTP Request Forgery issue was discovered in Varnish Cache 5.x and 6.x before 6.0.11, 7.x before 7.1.2, and 7.2.x before 7.2.1. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Varnish Cache, with HTTP/2 enabled, allows request smuggling and VCL authorization bypass via a large Content-Length header for a POST request. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This HTTP Request/Response Smuggling vulnerability could allow attackers to manipulate HTTP request interpretation between frontend and backend servers.
An issue was discovered in Varnish Cache before 6.0.6 LTS, 6.1.x and 6.2.x before 6.2.3, and 6.3.x before 6.3.2. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in Varnish Cache before 6.0.4 LTS, and 6.1.x and 6.2.x before 6.2.1. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in Varnish HTTP Cache 4.0.1 through 4.0.4, 4.1.0 through 4.1.7, 5.0.0, and 5.1.0 through 5.1.2. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.