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

High 7.5 Published 22 May 2026 Updated 18 Sep 2026

Attackers can cause denial of service via CPU exhaustion by sending crafted RSA or DSA public keys during authentication in the Go SSH library.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-39829?

CVE-2026-39829 is a high-severity denial of service vulnerability in golang.org/x/crypto/ssh, published on 22 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-347, CWE-1284

Which versions are affected by CVE-2026-39829?

3 open source packages ship an affected version, including golang.org/x/crypto. It affects 1 product.

Package	Affected	Fixed in
`golang.org/x/crypto` Go	All versions	`0.52.0`
`golang.org/x/crypto` Go	All versions	`0.52.0`
`golang.org/x/crypto` Go	All versions	`0.52.0`

Products include Golang Crypto.

How do I fix CVE-2026-39829?

Upgrade golang.org/x/crypto to 0.52.0 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-39829 being exploited?

There is no known exploitation of CVE-2026-39829 in the wild and no public exploit code.

Sources

Also known as AZL-87188, AZL-87251, AZL-87305, AZL-87396, AZL-87468, AZL-87618 and 1120 more.