# CVE-2026-77265: MCP Atlassian: SSRF via DNS Rebinding in Header-Based Authentication Flow

> Unauthenticated attackers can exploit DNS rebinding in MCP Atlassian to access internal services via crafted URL headers.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** GHSA-49xv-9743-pw8w, PYSEC-2026-4083

## What is CVE-2026-77265?

CVE-2026-77265 is a medium-severity server-side request forgery vulnerability in sooperset mcp-atlassian, published on 22 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, header-supplied Jira or Confluence URLs are resolved and validated before the HTTP client resolves the hostname again for the connection. An unauthenticated caller can use a DNS-rebinding hostname that returns a public address during validation and an internal address during connection, causing requests to internal or metadata services. The advisory traces the vulnerable input and processing flow through X-Atlassian-Jira-Url, X-Atlassian-Confluence-Url, validate_url_for_ssrf, and DNS rebinding, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-77265?

3 open source packages ship an affected version, including mcp-atlassian. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mcp-atlassian` | PyPI | All versions | 0.22.0 |
| `mcp-atlassian` | PyPI | All versions | 0.22.0 |
| `mcp-atlassian` | PyPI | All versions | 0.22.0 |

Products: Mcp-Atlassian Mcp Atlassian.

## How do I fix CVE-2026-77265?

Upgrade mcp-atlassian to 0.22.0 or later.

## Is CVE-2026-77265 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77265 exists.

## Other vulnerabilities in sooperset mcp-atlassian

- [CVE-2026-77244](https://insights.sbomify.com/CVE-2026-77244/): [mcp-atlassian] Authentication bypass in HTTP transport: AtlassianOpaqueTokenVerifier accepts any non-empty token (critical 10.0)
- [CVE-2026-77254](https://insights.sbomify.com/CVE-2026-77254/): MCP Atlassian: Unauthenticated HTTP MCP requests can use globally configured Jira and Confluence credentials (critical 9.1)
- [CVE-2026-27825](https://insights.sbomify.com/CVE-2026-27825/): MCP Atlassian has an arbitrary file write leading to arbitrary code execution via unconstrained download_path in confluence_download_attachment (critical 9.1)
- [CVE-2026-77243](https://insights.sbomify.com/CVE-2026-77243/): MCP Atlassian: ENABLED_TOOLS / Toolset authorization bypass (high 8.8)
- [CVE-2026-77274](https://insights.sbomify.com/CVE-2026-77274/): MCP Atlassian: SSRF Protection Bypass (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77265 and fix it if it is affected.

What it is: CVE-2026-77265 is a medium-severity server-side request forgery vulnerability in sooperset mcp-atlassian, published on 22 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77265 exists.

Affected packages and fixed versions:
- mcp-atlassian (PyPI): affected all versions; fixed in 0.22.0
- mcp-atlassian (PyPI): affected all versions; fixed in 0.22.0
- mcp-atlassian (PyPI): affected all versions; fixed in 0.22.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-77265/ (Markdown: https://insights.sbomify.com/CVE-2026-77265/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77265
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77265
- OSV: https://osv.dev/vulnerability/CVE-2026-77265

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77265/
Summaries are generated and may contain mistakes; the official description above is the record.