#VU104968 Input validation error in Phusion Passenger - CVE-2025-26803

Vulnerability identifier: #VU104968

Vulnerability risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2025-26803

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Phusion Passenger
Server applications / Application servers

Vendor: Phusion B.V.

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to insufficient validation of user-supplied input when parsing HTTP requests with invalid HTTP method. A remote attacker can send a specially crafted HTTP request to the application and perform a denial of service (DoS) attack.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Phusion Passenger: 6.0.21 - 6.0.25

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External links
https://blog.phusion.nl/2025/02/19/passenger-6-0-26/
https://github.com/phusion/passenger/commit/bb15591646687064ab2d578d5f9660b2a4168017
https://github.com/phusion/passenger/compare/release-6.0.25...release-6.0.26
https://github.com/phusion/passenger/releases/tag/release-6.0.26

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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.