ecdsautils is a tiny collection of programs used for ECDSA (keygen, sign, verify). `ecdsa_verify_[prepare_]legacy()` does not check whether the signature values `r` and `s` are non-zero. A signature consisting only of zeroes is always considered valid, making it trivial to forge signatures. Requiring multiple signatures from different public keys does not mitigate the issue: `ecdsa_verify_list_legacy()` will accept an arbitrary number of such forged signatures. Both the `ecdsautil verify` CLI command and the libecdsautil library are affected. The issue has been fixed in ecdsautils 0.4.1. All older versions of ecdsautils (including versions before the split into a library and a CLI utility) are vulnerable.
https://www.debian.org/security/2022/dsa-5132
https://lists.debian.org/debian-lts-announce/2022/05/msg00007.html
https://github.com/freifunk-gluon/ecdsautils/security/advisories/GHSA-qhcg-9ffp-78pw
https://github.com/freifunk-gluon/ecdsautils/commit/39b6d0a77414fd41614953a0e185c4eefa2f88ad
https://github.com/freifunk-gluon/ecdsautils/commit/1d4b091abdf15ad7b2312535b5b95ad70f6dbd08