# MCP Atlassian: SSRF via DNS Rebinding in Header-Based Authentication Flow

Advisory record · `GHSA-49xv-9743-pw8w`

- **Identifiers:** `GHSA-49xv-9743-pw8w` · `CVE-2026-77265` · `PYSEC-2026-4083`
- **State:** Confirmed
- **Severity:** CVSS 5.9 Medium
- **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, 20:35 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.

> Versions of mcp-atlassian before 0.22.0 are vulnerable to server-side request forgery through DNS rebinding in the header-based authentication flow. The SSRF check resolves the hostname once, but the actual request resolves it again later, so a remote, unauthenticated attacker could point the request at internal addresses such as cloud metadata services. The source describes the attack as probabilistic and limited to deployments that accept header-based personal access tokens. Upgrade to mcp-atlassian 0.22.0 or later. No workaround is listed.

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

- 5.9 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0029, the 21st 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-49xv-9743-pw8w)

## Sources

- [GitHub Advisory Database: GHSA-49xv-9743-pw8w](https://github.com/advisories/GHSA-49xv-9743-pw8w)
- [OSV: GHSA-49xv-9743-pw8w](https://osv.dev/vulnerability/GHSA-49xv-9743-pw8w)
- <https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-49xv-9743-pw8w>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-77265>
- <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-49xv-9743-pw8w>, 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-49xv-9743-pw8w/>. Everything for agents: <https://agentprime.io/llms.txt>.