Description
In GnuPG through 2.4.8, if a signed message has \f at the end of a plaintext line, an adversary can construct a modified message that places additional text after the signed material, such that signature verification of the modified message succeeds (although an "invalid armor" message is printed during verification). This is related to use of \f as a marker to denote truncation of a long plaintext line.
Affected products
gnupg: gnupg
References4
- gpg.fail/formfeed Product
- media.ccc.de/v/39c3-to-sign-or-not-to-sign-practical-vulnerabil… Product
- news.ycombinator.com/item?id=46404339 Issue Tracking
- gpg.fail/formfeed Product
Metrics
- CVSS 3.1
-
4.7
MEDIUM
Score source: NVD
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N - EPSS — exploit probability
- 0% percentile: 1 · as of 11 November 2026
- CWE
- CWE-347
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.