Inconsistent interpretation of HTTP requests in Varnish Enterprise and Varnish Cache - CVE-2025-30346

Vulnerability identifier: #VU105850

CSH Severity: Medium

CVSS v4: 6.9 [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]

CVE-ID: CVE-2025-30346

CWE-ID: CWE-444

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to perform HTTP request smuggling attacks.

The vulnerability exists due to improper validation of HTTP/1 client-side desync requests. A remote attacker can send a specially crafted HTTP request to the server and smuggle arbitrary HTTP headers.

Successful exploitation of vulnerability may allow an attacker to poison HTTP cache and perform phishing attacks.

Varnish Enterprise
Varnish Cache
openEuler
Fedora
varnish
varnish-debuginfo
varnish-debugsource
varnish-devel
varnish-help

Install updates from vendor's website.

Varnish Enterprise - update to 6.0.13r13
Varnish Cache - addressed in versions 7.6.2, 7.7.0
varnish - update to 7.4.3-2
varnish-debuginfo - update to 7.4.3-2
varnish-debugsource - update to 7.4.3-2
varnish-devel - update to 7.4.3-2
varnish-help - update to 7.4.3-2
varnish - addressed in versions 7.5.0-3.fc41, 7.6.1-5.fc42

• https://docs.varnish-software.com/security/VSV00015

• HTTP request smuggling in Varnish Cache and Varnish Enterprise
• Fedora 42 update for varnish
• Fedora 41 update for varnish
• openEuler update for varnish