# Prevent DoS on deadlocked undecided channel in golang.org/x/crypto/ssh

Advisory record · `GO-2026-6354`

- **Identifiers:** `GO-2026-6354` · `CVE-2026-78662`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-770](https://cwe.mitre.org/data/definitions/770.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Published:** 2 Sept 2026
- **Updated:** 3 Sept 2026
- **Reviewed by a person:** No

Published by OSV at 2 Sept 2026, 19:12 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `golang.org/x/crypto` (Go): affected `<0.56.0`; fixed in `0.56.0`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Golang.org/x/crypto/ssh is vulnerable in versions before 0.56.0. A malicious peer can flood a channel that has not yet been established, which deadlocks the whole SSH connection. Upgrade golang.org/x/crypto to version 0.56.0 or later.

Written 6 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`, from ADP (CISA-ADP)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0043, the 37th percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:46 UTC: First seen by agentprime
- 31 Oct 2026, 14:46 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GO-2026-6354)

## Sources

- [OSV: GO-2026-6354](https://osv.dev/vulnerability/GO-2026-6354)
- <https://go.dev/cl/826504>
- <https://groups.google.com/g/golang-announce/c/1y3fb2np35U>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GO-2026-6354>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GO-2026-6354/>. Everything for agents: <https://agentprime.io/llms.txt>.