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Vulnerability Database

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A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

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Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

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361,925

Total vulnerabilities in the database

MCP Atlassian: DNS-rebinding TOCTOU bypass of the SSRF fix (CVE-2026-27826) — mcp-atlassian

Server-Side Request Forgery (SSRF)

Summary

GHSA-7r34-79r5-rcc9's fix added validate_url_for_ssrf, which resolves the attacker-controlled X-Atlassian-{Jira,Confluence}-Url header host once at middleware time and trusts the result. But the outbound request is later built with the raw hostname and re-resolves at connect time with no IP pinning. An attacker-controlled rebinding DNS name returns a public IP on the guard's lookup (validation passes) and 169.254.169.254 / an internal IP on the request's lookup (the socket connects there) → unauthenticated SSRF to cloud metadata / internal services on the patched build.

Relationship to CVE-2026-27826 / GHSA-7r34-79r5-rcc9 (incomplete fix — please read first)

This is an incomplete-fix sibling of the published GHSA-7r34-79r5-rcc9 (the X-Atlassian-*-Url header SSRF). That fix (PR #986/#1005) added a single middleware-time resolve + allowlist DNS-skip, but does not pin the validated IP to the connection — the fetcher re-resolves the raw hostname at connect time, so the documented SSRF mitigation is incomplete against DNS-rebinding. The other advisory GHSA-xjgw-4wvw-rgm4 (file-write) is unrelated. Verified live (2026-06-27): neither advisory, nor any open PR/issue (rebind/TOCTOU/getaddrinfo/pin → 0), covers connect-time re-resolution. Filing as an incomplete-fix of GHSA-7r34 (not a standalone fresh SSRF).

Affected

src/mcp_atlassian/utils/urls.py + servers/main.py + servers/dependencies.py, HEAD ba72540 (PyPI mcp-atlassian, patched ≥0.17.0). CWE-918 (SSRF) via CWE-367 (TOCTOU).

Vulnerable code

utils/urls.py validate_url_for_ssrf (≈184-205) resolves + validates, then returns a string verdict, not a pinned IP:

def validate_url_for_ssrf(url: str) -&gt; str | None:   # returns an error string or None — NO IP is pinned
    ...
    # resolves the host, checks each resolved IP is global, then DISCARDS the IP

servers/main.py:526,534 calls it once in middleware. servers/dependencies.py:544-561 then builds the fetcher with url = <raw header hostname> (no pinned IP, no custom resolver / cached-getaddrinfo adapter), so the actual request re-resolves the name.

PoC (executed — boundary demonstration)

The PoC loads the real urls.py by path (importlib, sha256 printed) and drives the genuine validate_url_for_ssrf, simulating the two resolutions via getaddrinfo:

[CHECK ] validate_url_for_ssrf(&#039;http://rebind.attacker.example&#039;) -&gt; None        (getaddrinfo#1 = 93.184.216.34 global -&gt; guard PASSED)
[CONNECT] getaddrinfo call #2 returned 169.254.169.254 -&gt; the socket connects HERE
[PROOF ] guard validated IP 93.184.216.34 but connection targets 169.254.169.254  =&gt; SSRF on the PATCHED build
[CONTROL] if guard SAW 169.254.169.254 at check time -&gt; blocks it correctly
[PIN   ] validate_url_for_ssrf returns a verdict (None), NOT an IP; dependencies.py builds url=raw hostname -&gt; NO pin
ALL PoC ASSERTIONS PASSED — DNS-rebind TOCTOU bypass demonstrated.

Honest scope of the PoC: this is a boundary demonstration — it proves the structural TOCTOU (the guard validates an IP it then discards; the connection re-resolves an unpinned hostname). It does not demonstrate a live end-to-end SSRF on a running server; that additionally requires an attacker-controlled fast-rebinding authoritative DNS responder winning the resolve→connect window. Flagging this explicitly rather than overclaiming.

Impact

Same as parent GHSA-7r34 (unauth read of cloud-metadata IAM creds / internal-service reach), reachable again on the patched version. The X-Atlassian-*-Url headers are processed in UserTokenMiddleware before fetcher creation, so an unauthenticated/low-priv caller controls the host.

Severity

High — CVSS v3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N ≈ 7.x, aligned to the parent (8.2) with AC:H for the rebinding-race precondition. Honest caveat (above): the executed PoC proves the missing IP-pin structurally; a live exploit additionally needs an attacker rebinding-DNS. Not Critical.

Remediation

Pin the connection to the IP that validate_url_for_ssrf validated: use a custom resolver / cached-getaddrinfo requests-adapter (or pass the validated IP with a Host header), so the connect cannot re-resolve to a different address.

Dedup / freshness (re-verified live 2026-06-27)

Advisories GHSA-7r34-79r5-rcc9 (original header SSRF this bypasses) + GHSA-xjgw-4wvw-rgm4 (file-write, unrelated). Neither covers connect-time re-resolution / rebinding. PR #986/#1005 (the fix) add a single middleware-time resolve + allowlist DNS-skip, no pinning. gh search prs/issues for rebind/TOCTOU/getaddrinfo/pin → 0. First-party code. Fresh at HEAD ba72540.

Published: Jul 10, 2026
Updated: Jul 11, 2026
GHSA: GHSA-489g-7rxv-6c8q
Severity: Medium
Exploit:
CISA KEV:

CVSS v3:

Severity: Medium
Score: 6.5
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N

CWEs:

CWE-918

Affected Software
References

Software	From	Fixed in
mcp-atlassian	-	0.22.0

https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-489g-7rxv-6c8q

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.