The Crypt::DSA Perl module versions prior to 1.21 suffer from a nonce reuse vulnerability in the signing process. Specifically, the Crypt::DSA::sign function caches the per-signature nonce in the Key object and does not clear it after use. Consequently, the first signature generates a nonce, but subsequent signatures with the same Key object reuse this nonce, resulting in identical 'r' values in signatures. This nonce reuse enables attackers to recover the private key, compromising the security of the signing key. Keys used to sign more than once with affected versions should be considered compromised.

An attacker who obtains multiple signatures generated by the same key object in affected versions can recover the private key due to nonce reuse. This compromises the confidentiality and integrity of cryptographic operations relying on the private key, allowing impersonation or signature forgery. The vulnerability does not affect availability.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid using Crypt::DSA versions prior to 1.21 for signing operations, or ensure that keys are not reused for multiple signatures. Consider regenerating keys if they have been used multiple times with affected versions, as they should be considered compromised.