Input validation error in Varnish Cache and Varnish Enterprise - #VU124839
Published: April 2, 2026
Vulnerability identifier: #VU124839
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
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 Enterprise
Varnish Cache
Varnish Enterprise
Detailed vulnerability description
The vulnerability allows a remote attacker to poison the cache or bypass authentication.
The vulnerability exists due to improper input validation in HTTP/1.1 request parsing when processing absolute form URIs. A remote attacker can send a specially crafted request with an absolute URL pointing to a root path (e.g., https://example.com/) to poison the cache or bypass authentication.
The attack is limited to root URLs with a path of /; deeper paths are not vulnerable.
Remediation
Install updates from vendor's website.