Input validation error in Varnish Cache - #VU132033
Published: May 21, 2026
Vulnerability identifier: #VU132033
CSH Severity: High
CVSS v4.0: 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
CVE-ID: N/A
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Varnish Software
Affected software:
Varnish Cache
Varnish Cache
Detailed vulnerability description
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 security update from vendor's website.