CVE-2026-50052: the vinyl cache project varnish cache (pre split) HTTP Request/Response Smuggling

Vulnerability summary

CVE-2026-50052 is a low (CVSS 2.3) HTTP Request/Response Smuggling vulnerability in the vinyl cache project varnish cache (pre split). EPSS estimates a 0.47% chance of exploitation in the next 30 days, higher than 39.6% of scored vulnerabilities.

Timeline

1. 03-06-2026
   PublishedVulnerability first disclosed.
2. 01-07-2026
   Last modifiedVulnerability information updated.

Description

In Vinyl Cache before 9.0.1 and Varnish Cache before 9.0.3, a deficiency in HTTP/2 request parsing can be exploited to launch a backend request desync attack (request smuggling), which in turn can be used for cache poisoning, authentication bypass, or possibly even information disclosure and manipulation. The attack vector only exists if HTTP/2 support is enabled by setting the feature parameter to contain +http2. HTTP/2 support is disabled by default.

• CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.