Signature verification bypass in GnuPG

1) Input validation error

EUVDB-ID: #VU106992

Risk: Medium

CVSSv4.0: 1.2 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2025-30258

CWE-ID: CWE-20 - Improper input validation

Exploit availability: No

Description

The vulnerability allows a remote attacker to disable signature verification.

The vulnerability exists due to an error when handling subkey data. A remote attacker can trick the victim into importing a specially crafted certificate with subkey data that lacks a valid backsig or that has incorrect usage flags and disable signature verification for other signing keys.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

GnuPG: 2.0 - 2.6

CPE2.3

• cpe:2.3:a:gnu:gnupg:2.0:*:*:*:*:*:*:*
• cpe:2.3:a:gnu:gnupg:2.0.0:*:*:*:*:*:*:*
• cpe:2.3:a:gnu:gnupg:2.0.1:*:*:*:*:*:*:*

External links

https://dev.gnupg.org/rG48978ccb4e20866472ef18436a32744350a65158
https://dev.gnupg.org/T7527
https://lists.gnupg.org/pipermail/gnupg-announce/2025q1/000491.html

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.