# MCP Atlassian: SSRF Protection Bypass

Advisory record · `GHSA-hgcf-4mq8-5266`

- **Identifiers:** `GHSA-hgcf-4mq8-5266` · `CVE-2026-77274` · `PYSEC-2026-4096`
- **State:** Confirmed
- **Severity:** CVSS 8.8 High
- **Critical:** No
- **Weakness (CWE):** [CWE-918](https://cwe.mitre.org/data/definitions/918.html)
- **Tags:** [Server-side request forgery (SSRF)](https://agentprime.io/advisories/tag/ssrf.md)
- **Published:** 22 Sept 2026
- **Updated:** 1 Oct 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 22 Sept 2026, 20:36 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `mcp-atlassian` (PyPI): affected `<0.22.0`; fixed in `0.22.0`

## Machine-written summary

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

> The SSRF validation in mcp-atlassian versions before 0.22.0 can be bypassed with a crafted URL containing a backslash before userinfo-like syntax, so the URL check validates one host while requests go to another. An attacker who can supply the X-Atlassian-Jira-Url or X-Atlassian-Confluence-Url header can make the server send requests to loopback or internal services. Upgrade to mcp-atlassian 0.22.0 or later. The source gives few details on the exact trigger conditions.

Written 1 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

- 8.8 High, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0033, the 26th percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:09 UTC: First seen by agentprime
- 31 Oct 2026, 14:09 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-hgcf-4mq8-5266)

## Sources

- [GitHub Advisory Database: GHSA-hgcf-4mq8-5266](https://github.com/advisories/GHSA-hgcf-4mq8-5266)
- [OSV: GHSA-hgcf-4mq8-5266](https://osv.dev/vulnerability/GHSA-hgcf-4mq8-5266)
- <https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-hgcf-4mq8-5266>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-77274>
- <https://github.com/sooperset/mcp-atlassian/pull/1448>
- <https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460>
- <https://github.com/sooperset/mcp-atlassian>
- <https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0>

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/GHSA-hgcf-4mq8-5266>, 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/GHSA-hgcf-4mq8-5266/>. Everything for agents: <https://agentprime.io/llms.txt>.