CVE-2026-34475
MediumCVSS 5.4Exploitation Probability (EPSS)
Low risk11th percentile - higher than 11% of all known CVEs
Summary
Varnish Cache before 8.0.1 and Varnish Enterprise before 6.0.16r12, in certain unchecked req.url scenarios, mishandle URLs with a path of / for HTTP/1.1. This may lead to cache poisoning or authentication bypass.
Risk Assessment
Cache poisoning can serve malicious content to other users, and authentication bypass may allow unauthorized access to protected resources.
Recommendation
Update Varnish Cache to version 8.0.1 or later and Varnish Enterprise to 6.0.16r12 or later. Review VCL rules for req.url handling.
Other vulnerabilities in Varnish Cache
See all- CVE-2026-50052Low
In Vinyl Cache before 9.0.1 and Varnish Cache before 9.0.3, a deficiency in HTTP/2 request parsing can be exploited for backend request desync (request smuggling), leading to cache poisoning, authentication bypass, or information disclosure. The attack only works if HTTP/2 is enabled (disabled by default).
- CVE-2026-40396Medium
Varnish Cache 9 before 9.0.1 allows a "workspace overflow" denial of service (daemon panic) after timeout_linger. A malicious client could send an HTTP/1 request, wait until the session releases its worker thread (timeout_linger), and resume traffic before the session is closed (timeout_idle) by sending more than one request at once to trigger pipelining and workspace overflow. The vulnerability stems from a porting error of the non-blocking architecture from Varnish Enterprise.
- CVE-2026-40394Medium
Varnish Cache 9 before 9.0.1 and Varnish Enterprise before 6.0.16r11 allow a "workspace overflow" denial of service (daemon panic) for certain amounts of prefetched data. During HTTP/2 upgrade, a buffer allocation splits the workspace, and the next fetch may run out of workspace.
Original NVD description (English source)
Varnish Cache before 8.0.1 and Varnish Enterprise before 6.0.16r12, in certain unchecked req.url scenarios, mishandle URLs with a path of / for HTTP/1.1, potentially leading to cache poisoning or authentication bypass.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS