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Security Digest · Vulnerability record

CVE-2026-39832: golang.org/x/crypto doesn't drop invoking agent constraints when forwarding keys

When adding a key to a remote agent constraint extensions such as restrict-destination-v00@openssh.com were not serialized in the request.

CVSS 8.7 High EPSS 0.7% · p53

Updated By erroneo.us Security Desk45 references Seen in the digest for Jun 25, 2026

Should you act?

Normal patch cycle

No exploitation signal; fix it in your next routine update if you are affected. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

  • No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
  • EPSS 0.7%, percentile 53: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 53% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
  • Needs an account (low (any account)). Exposure depends on who can log in.
  • Only applies if your dependency tree includes golang.org/x/crypto (Go) < 0.52.0, fixed in 0.52.0. Check your lockfile, including transitive dependencies.

What it is

When adding a key to a remote agent constraint extensions such as restrict-destination-v00@openssh.com were not serialized in the request. Destination restrictions were silently stripped when forwarding keys, allowing unrestricted use of the key on the remote host. The client now serializes all constraint extensions. Additionally, the in-memory keyring returned by NewKeyring() now rejects keys with unsupported constraint extensions instead of silently ignoring them.

From the GitHub advisory

When adding a key to a remote agent constraint extensions such as restrict-destination-v00@openssh.com were not serialized in the request. Destination restrictions were silently stripped when forwarding keys, allowing unrestricted use of the key on the remote host. The client now serializes all constraint extensions. Additionally, the in-memory keyring returned by NewKeyring() now rejects keys with unsupported constraint extensions instead of silently ignoring them.

Weakness type: CWE-281, CWE-502.

Product: golang.org/x/crypto (Go) · Assigned by: Go · Published: 2026-05-22

Affected and fixed versions

EcosystemPackageVulnerableFirst fixed
Gogolang.org/x/crypto< 0.52.00.52.0
VendorProductAffected versions (per CVE record)
golang.org/x/cryptogolang.org/x/crypto/ssh/agent< 0.52.0

Severity scores

Scored byCVSSScoreVector
CISA-ADP3.19.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
redhat-SADP3.18.7 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
GitHub3.19.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
  • Attack vector: network (remotely reachable)
  • Attack complexity: low
  • Privileges required: low (any account)
  • User interaction: required (a user must click/open something)
  • Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

  • CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
  • CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
  • FIRST EPSS (model of 2026-10-21): 0.72% probability of exploitation activity in the next 30 days; percentile 53.

Timeline

  • — CVE record published by Go
  • — GitHub-reviewed advisory GHSA-f5wc-c3c7-36mc published (critical)
  • — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

  1. access.redhat.com access.redhat.com
  2. access.redhat.com access.redhat.com
  3. access.redhat.com access.redhat.com
  4. access.redhat.com access.redhat.com
  5. access.redhat.com access.redhat.com
  6. access.redhat.com access.redhat.com
  7. access.redhat.com access.redhat.com
  8. access.redhat.com access.redhat.com
  9. access.redhat.com access.redhat.com
  10. access.redhat.com access.redhat.com
  11. access.redhat.com access.redhat.com
  12. access.redhat.com access.redhat.com
  13. access.redhat.com access.redhat.com
  14. access.redhat.com access.redhat.com
  15. access.redhat.com access.redhat.com
  16. access.redhat.com access.redhat.com
  17. access.redhat.com access.redhat.com
  18. access.redhat.com access.redhat.com
  19. access.redhat.com access.redhat.com
  20. access.redhat.com access.redhat.com
  21. access.redhat.com access.redhat.com
  22. access.redhat.com access.redhat.com
  23. access.redhat.com access.redhat.com
  24. access.redhat.com access.redhat.com
  25. access.redhat.com access.redhat.com
  26. access.redhat.com access.redhat.com
  27. access.redhat.com access.redhat.com
  28. access.redhat.com access.redhat.com
  29. access.redhat.com access.redhat.com
  30. access.redhat.com access.redhat.com
  31. access.redhat.com access.redhat.com
  32. access.redhat.com access.redhat.com
  33. access.redhat.com access.redhat.com

Vulnerability records

  1. GitHub Advisory GHSA-f5wc-c3c7-36mc github.com
  2. CVE.org record CVE-2026-39832 cve.org
  3. NVD entry CVE-2026-39832 nvd.nist.gov

Other references from the CVE record and advisory

  1. go.dev go.dev
  2. go.dev go.dev
  3. go.dev go.dev
  4. groups.google.com groups.google.com
  5. pkg.go.dev pkg.go.dev
  6. access.redhat.com access.redhat.com
  7. RHBZ#2480685 bugzilla.redhat.com
  8. security.access.redhat.com security.access.redhat.com
  9. go.dev go.dev

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