Re: Retrospective by 'gpg.fail' authors
GnuPG's Werner Koch says gpg.fail samples only crash GnuPG via DER-as-printf format string in --debug x509; RCE claim remains unproven.
Werner Koch replied to the gpg.fail retrospective, noting that GnuPG versions above 2.2 produce garbled stderr or crash when the project's certificates are used with --debug x509 because DER data is passed as a printf format string. Testing the certificates from the researchers' Git repo yielded only a segfault, not demonstrated code execution. Koch states how remote code execution would be achieved is unclear and asks for a real reproducer.
- Format string flaw: DER certificate used as printf format
- Only a segfault reproduced so far; RCE unverified
- Affects --debug x509 path in GnuPG versions > 2.2
Posted by Werner Koch on Sep 15 Hi! On Mon, 14 Sep 2026 21:28, Clemens Lang said: Actually in all versions > 2.2 if you use --debug x509. The result is that you get garbled output on stderr. Using the certificates from their Git repo we have not been able to get more than a segv. That is obvious because the DER is used as printf format string. How it is possible to get a an RCE is not clear to me - at least not with the sample certificate. We need a real reproducers....
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