CVE-2026-39829: Invoking pathological RSA/DSA parameters may cause DoS in golang.org/x/crypto/ssh

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-22 · updated 2026-09-16
Weakness: CWE-347

Description

The RSA and DSA public key parsers did not enforce size limits on key parameters. A crafted public key with an excessively large modulus or DSA parameter could cause several minutes of CPU consumption during signature verification. This could be triggered by unauthenticated clients during public key authentication. RSA moduli are now limited to 8192 bits, and DSA parameters are validated per FIPS 186-2.

Affected products

golang.org/x/crypto/ssh: before 0.52.0 — fixed in 0.52.0
Golang.Org/X/Crypto: before 0.52.0 — fixed in 0.52.0

How to fix

Upgrade to a fixed version: golang.org/x/crypto/ssh 0.52.0; Golang.Org/X/Crypto 0.52.0. Check the vendor advisory for mitigations.

References

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