GHSA-4cc2-g9w2-fhf6 is a medium-severity (CVSS 5.9) Server-Side Request Forgery (SSRF) vulnerability in zeep. O3 Security confirms whether GHSA-4cc2-g9w2-fhf6 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Zeep: Server-Side Request Forgery (SSRF)
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-4cc2-g9w2-fhf6.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-4cc2-g9w2-fhf6 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 0 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
zeepReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
When parsing a WSDL or XSD document, python-zeep follows transitive references — xsd:import, xsd:include, wsdl:import, and lxml entity/DTD resolution — and will fetch http/https URLs found in those references. The Settings.forbid_external option, intended to disable this transitive remote fetching, was defined but not wired to any logic from version 4.0.0 through 4.3.2 (a regression introduced when zeep moved off defusedxml in 4.0). As a result, setting forbid_external=True had no effect, and applications that processed untrusted or attacker-influenced WSDL/XSD documents could be coerced into making server-side requests to arbitrary URLs (SSRF).
Impact
Server-Side Request Forgery (SSRF), CWE-918.
An attacker who can supply or influence the contents of a WSDL/XSD that an application loads with zeep can embed an import/include reference (e.g. <xsd:import schemaLocation="http://169.254.169.254/...">) pointing at an internal or otherwise sensitive endpoint. When zeep parses the document it transitively fetches that URL using the configured transport, causing the application to issue outbound requests to attacker-chosen destinations. This can be used to reach internal-only services, cloud metadata endpoints, or other hosts not directly reachable by the attacker, and may disclose response timing/behaviour.
Impacted users are those who:
- load WSDL/XSD documents that are untrusted or whose import targets an attacker can control, and/or
- relied on
forbid_external=Trueas a security control — in 4.0.0–4.3.2 that setting silently did nothing, so the protection users believed they had was not in effect.
Note the default was (and remains) forbid_external=False, i.e. transitive remote fetching is permitted by default; the security defect is specifically that the opt-out control was non-functional.
Patches
Fixed in python-zeep 4.3.3. The forbid_external setting is now enforced: when set to True, zeep refuses to transitively fetch http/https resources via xsd:import, xsd:include, wsdl:import, or lxml entity/DTD resolution, raising zeep.exceptions.ExternalReferenceForbidden. The user-supplied entry-point WSDL/schema URL is still loaded.
Affected versions: >= 4.0.0, < 4.3.3.
Upgrade to 4.3.3 (or later) and set forbid_external=True when loading documents from untrusted sources:
from zeep import Client, Settings
settings = Settings(forbid_external=True)
client = Client("https://untrusted.example/service?wsdl", settings=settings)
Workarounds
If you cannot upgrade to 4.3.3:
- Do not load untrusted WSDL/XSD documents, and avoid loading WSDLs whose import/include targets can be influenced by untrusted input.
- Vendor the schema locally: pre-fetch and review the WSDL and all of its imported schemas, then load them from local files (e.g. file:// paths) so no remote fetching occurs at parse time.
- Restrict egress at the network layer: block outbound traffic from the host/process to internal ranges and metadata endpoints (e.g. 169.254.169.254, RFC1918 ranges) so SSRF attempts cannot reach sensitive targets.
- Use a restrictive custom Transport: subclass the zeep transport and reject/allow-list URLs in load() so disallowed hosts are never fetched.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | zeep | ≥ 4.0.0&&< 4.3.3 | 4.3.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for zeep. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update zeep to 4.3.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4cc2-g9w2-fhf6 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-4cc2-g9w2-fhf6 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-4cc2-g9w2-fhf6. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-4cc2-g9w2-fhf6 in your dependencies?
O3 detects GHSA-4cc2-g9w2-fhf6 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.