SB2026052122 - Remote denial of service in Varnish Cache

Description

This security bulletin contains information about 1 vulnerability.

1) Input validation error (CVE-ID: N/A)

CWE-ID: CWE-20 - Improper input validation

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber

The vulnerability allows a remote attacker to poison the cache, bypass authentication, or disclose sensitive information.

The vulnerability exists due to improper input validation in the HTTP/2 request parser when processing HTTP/2 requests with crafted request framing that causes backend request desynchronization. A remote attacker can send a specially crafted HTTP/2 request to poison the cache, bypass authentication, or disclose sensitive information.

The attack vector exists only when HTTP/2 support is enabled with the +http2 feature parameter.

Remediation

Install update from vendor's website.

References

• https://docs.varnish-software.com/security/VSV00019
• https://vinyl-cache.org/security/VSV00019.html