#VU105850 Inconsistent interpretation of HTTP requests in Varnish Enterprise and Varnish Cache - CVE-2025-30346

Vulnerability identifier: #VU105850

Vulnerability risk: Medium

CVSSv4.0: 2.7 [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: CVE-2025-30346

CWE-ID: CWE-444

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Varnish Enterprise
Server applications / IDS/IPS systems, Firewalls and proxy servers
Varnish Cache
Server applications / IDS/IPS systems, Firewalls and proxy servers

Vendor: Varnish Software

Description

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.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Varnish Enterprise: 6.0.0r0 - 6.0.13r12

Varnish Cache: 7.5.0, 7.6.0 - 7.6.1

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External links
https://docs.varnish-software.com/security/VSV00015

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.