erroneo.us
Search all guides⌘K

Security Digest · Vulnerability record

CVE-2026-39830: golang.org/x/crypto: Invoking client can cause server deadlock on unexpected responses

A malicious SSH peer could send unsolicited global request responses to fill an internal buffer, blocking the connection's read loop.

CVSS 7.5 High EPSS 0.6% · p49

Updated By erroneo.us Security Desk63 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 0.6%, percentile 49: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 49% of all scored CVEs (low). EPSS is a probability, not a verdict.
  • Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
  • 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

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.

From the GitHub advisory

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.

Weakness type: CWE-772, CWE-119.

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< 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:N/A:H
redhat-SADP3.17.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub3.19.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
  • Attack vector: network (remotely reachable)
  • Attack complexity: low
  • Privileges required: none (no login)
  • User interaction: none
  • Scope: unchanged

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 partial.
  • FIRST EPSS (model of 2026-10-21): 0.62% probability of exploitation activity in the next 30 days; percentile 49.

Timeline

  • — CVE record published by Go
  • — GitHub-reviewed advisory GHSA-vgwf-h737-ff37 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
  34. access.redhat.com access.redhat.com
  35. access.redhat.com access.redhat.com
  36. access.redhat.com access.redhat.com
  37. access.redhat.com access.redhat.com
  38. access.redhat.com access.redhat.com
  39. access.redhat.com access.redhat.com
  40. access.redhat.com access.redhat.com
  41. access.redhat.com access.redhat.com
  42. access.redhat.com access.redhat.com
  43. access.redhat.com access.redhat.com
  44. access.redhat.com access.redhat.com
  45. access.redhat.com access.redhat.com
  46. access.redhat.com access.redhat.com
  47. access.redhat.com access.redhat.com
  48. access.redhat.com access.redhat.com
  49. access.redhat.com access.redhat.com
  50. access.redhat.com access.redhat.com
  51. access.redhat.com access.redhat.com
  52. access.redhat.com access.redhat.com

Vulnerability records

  1. GitHub Advisory GHSA-vgwf-h737-ff37 github.com
  2. CVE.org record CVE-2026-39830 cve.org
  3. NVD entry CVE-2026-39830 nvd.nist.gov

Other references from the CVE record and advisory

  1. go.dev go.dev
  2. groups.google.com groups.google.com
  3. go.dev go.dev
  4. go.dev go.dev
  5. pkg.go.dev pkg.go.dev
  6. access.redhat.com access.redhat.com
  7. RHBZ#2480684 bugzilla.redhat.com
  8. security.access.redhat.com security.access.redhat.com

Critical Go advisories · Today’s Security Digest