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

Source: https://junglewise.ai/threats/cve-2026-39829-go-x-crypto-ssh-denial-of-service-in-public-key-parsing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-22. Updated: 2026-06-25  
License: CC BY 4.0 with a link back

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)](https://junglewise.ai/threats/technologies/golang-org-x-crypto), [golang.org/x/crypto/ssh (Go)](https://junglewise.ai/threats/technologies/golang-org-x-crypto-ssh). Vendors: [Go](https://junglewise.ai/threats/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

  ```sh
  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

- [https://go.dev/cl/781641](https://go.dev/cl/781641)
- [https://go.dev/cl/781661](https://go.dev/cl/781661)
- [https://go.dev/issue/79565](https://go.dev/issue/79565)
- [https://groups.google.com/g/golang-announce/c/a082jnz-LvI](https://groups.google.com/g/golang-announce/c/a082jnz-LvI)
- [https://pkg.go.dev/vuln/GO-2026-5018](https://pkg.go.dev/vuln/GO-2026-5018)

## Related threats

- [Go SSH deadlock vulnerability in channel handling](https://junglewise.ai/threats/cve-2026-56855-go-ssh-deadlock-vulnerability-in-channel-handling)
- [Go x/crypto/ssh deadlock denial of service on undecided channel](https://junglewise.ai/threats/cve-2026-78662-go-2026-6354-prevent-dos-on-deadlocked-undecided-channel-in)
- [Go SSH source-address permission validation bypass in authentication callbacks](https://junglewise.ai/threats/cve-2026-56854-go-ssh-source-address-permission-validation-bypass-in)
- [GO-2026-5932 - The golang.org/x/crypto/openpgp package is unmaintained, unsafe by design, and has known security issues](https://junglewise.ai/threats/go-2026-5932-the-golang-org-x-crypto-openpgp-package-is-unmaintained-7e8ca4de)
- [Go x/crypto denial of service in SSH agent Ed25519 parsing](https://junglewise.ai/threats/cve-2026-46598-go-x-crypto-denial-of-service-in-ssh-agent-ed25519-parsing)