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VulnerabilityPublished Updated

CVE-2026-42508: golang.org/x/crypto/ssh/knownhosts · Improper Certificate Validation

Affects golang.org/x/crypto/ssh/knownhostsSource CVE Database V5

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Not known to be exploited · CVSS 9.1 Critical : upgrade to 0.52.0 as a priority.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
9.1Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
6.9% chance of exploitation in 30 days – higher than 94% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.52.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 22 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade golang.org/x/crypto/ssh/knownhosts to 0.52.0.

Affected software

ProductAffectedFixed in
golang.org/x/cryptogolang.org/x/crypto/ssh/knownhostsAffected
  • <0.52.0
Fixed in
  • 0.52.0
Gogolang.org/x/crypto/ssh/knownhostspkg:golang/golang.org/x/crypto/ssh/knownhostsOther threatsAffected
  • =0
Fixed in–
Gogolang.org/x/crypto/ssh/knownhostspkg:golang/golang.org/x/crypto/ssh/knownhostsOther threatsAffected
  • <0.52.0
Fixed in
  • 0.52.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Red Hat has issued advisories acknowledging the vulnerability and is working on fixes. Users should monitor the Red Hat advisory pages and apply updates once available. If you cannot patch yet, users should consider mitigating exposure by restricting access to affected systems and monitoring for suspicious activity related to SSH key usage. Consult the vendor advisory for the latest remediation guidance and update instructions.

Description

Previously, a revoked 'SignatureKey' belonging to a CA was not correctly checked for revocation. Now, both the 'key' and 'key.SignatureKey' are checked for @revoked.

References

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