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VulnerabilityPublished Updated

CVE-2026-39830: golang.org/x/crypto/ssh · Deadlock

Affects golang.org/x/crypto/sshSource 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
0.6% chance of exploitation in 30 days – higher than 52% 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:N/A:H

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 to 0.52.0.

Affected software

ProductAffectedFixed in
golang.org/x/cryptogolang.org/x/crypto/sshAffected
  • <0.52.0
Fixed in
  • 0.52.0
Gogolang.org/x/crypto/sshpkg:golang/golang.org/x/crypto/sshOther threatsAffected
  • =0
Fixed in–
Gogolang.org/x/crypto/sshpkg:golang/golang.org/x/crypto/sshOther 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

The vendor advisory recommends restricting network access to any service utilizing the golang.org/x/crypto/ssh library exposed to untrusted networks. Implement firewall rules to allow connections only from trusted hosts or networks. Restarting the affected service may be necessary for the new network rules to take effect.

Description

A malicious SSH peer could send unsolicited global request responses to fill an internal buffer, blocking the connection's read loop. The blocked goroutine could not be released by calling Close(), resulting in a resource leak per connection. Unsolicited global responses are now discarded.

References

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