CVE-2026-39829: Go x/crypto/ssh denial of service in public key parsing

CVE-2026-39829 · Severity: high · CVSS 7.5 · Published 2026-05-22

A vulnerability in the Go SSH library could allow an attacker to crash or slow down a server by sending a specially crafted security key. This component is widely used to secure remote access and data transfers in Go-based applications. An exploit could lead to a denial-of-service, making the affected service unavailable to legitimate users for several minutes at a time.

Technologies: golang.org/x/crypto (Go), golang.org/x/crypto/ssh (Go). Vendors: Go.

Quick answers

Is CVE-2026-39829 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-39829 being exploited in the wild.
How severe is CVE-2026-39829?
High severity, with a CVSS score of 7.5, published 22 May 2026.
Which products and versions are affected?
golang.org/x/crypto (Go) SEMVER:introduced=0,fixed=0.52.0; golang.org/x/crypto/ssh (Go) < 0.52.0.
Is there a fix for CVE-2026-39829?
Yes. golang.org/x/crypto (Go): upgrade to 0.52.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-39829 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-39829?
Check whether you run golang.org/x/crypto (Go) or golang.org/x/crypto/ssh (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • golang.org/x/crypto (Go): upgrade to 0.52.0 or later
    go get golang.org/x/crypto@v0.52.0

Technical details

A denial-of-service (DoS) vulnerability exists in the golang.org/x/crypto/ssh package due to improper verification of cryptographic signature parameters (CWE-347). The RSA and DSA public key parsers fail to enforce size limits on key parameters, such as the modulus. An unauthenticated remote attacker can trigger this by providing a crafted public key with excessively large parameters during the public key authentication phase. This results in several minutes of CPU exhaustion during signature verification. The issue is resolved in version 0.52.0 by limiting RSA moduli to 8192 bits and validating DSA parameters according to FIPS 186-2.

Affected products

  • Go golang.org/x/crypto/ssh < 0.52.0

Identifiers

  • CVE-2026-39829
  • GHSA-w879-237q-wc7r
  • GO-2026-5018

Timeline

  • 2026-05-22: advisory: NVD and Go Project published the vulnerability details.
  • 2026-06-25: patched: GitHub Advisory Database reviewed and published the advisory for version 0.52.0.

References

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