CVE-2026-39831: golang.org/x/crypto/ssh · Authentication Bypass by Spoofing
Affects golang.org/x/crypto/sshSource CVE Database V5
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
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 41% 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:NExploitation evidence
Disclosed: evidence found.
CVE published 22 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| golang.org/x/cryptogolang.org/x/crypto/ssh | Affected
| Fixed in
|
Gogolang.org/x/crypto/sshpkg:golang/golang.org/x/crypto/sshOther threats | Affected
| Fixed in– |
Gogolang.org/x/crypto/sshpkg:golang/golang.org/x/crypto/sshOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Mitigation can be applied by returning a specific extension in Permissions.Extensions to enforce user presence checks. If you cannot patch yet, implement this mitigation if possible.
Description
A critical authentication bypass vulnerability (CVE-2026-39831) exists in golang.org/x/crypto/ssh affecting FIDO/U2F security key types. The Verify() method fails to check the User Presence flag, allowing signatures generated without physical user interaction to be accepted. This flaw enables unauthorized use of hardware security keys without user touch unless mitigated by a specific extension in Permissions.Extensions. The vulnerability has a high CVSS score of 9.1 and impacts authentication security.