CVE-2026-40991
MEDIUMCVE-2026-40991 is a medium-severity (CVSS 5.9) XML External Entity (XXE) vulnerability in org.springframework.restdocs:spring-restdocs-webtestclient. O3 Security confirms whether CVE-2026-40991 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
XML External Entity (XXE) injection when documenting untrusted XML content
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 CVE-2026-40991.
Real-World Exposure
org.springframework.restdocs:spring-restdocs-webtestclient☕org.springframework.restdocs:spring-restdocs-webtestclient☕org.springframework.restdocs:spring-restdocs-webtestclient☕org.springframework.restdocs:spring-restdocs-restassured☕org.springframework.restdocs:spring-restdocs-restassured☕org.springframework.restdocs:spring-restdocs-restassuredReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
When using spring-restdocs-webtestclient or spring-restdocs-restassured to document a remote API accessed over HTTP, an attacker who compromises the API or tricks the user into documenting a malicious API can perform an XXE injection attack when the documentation-generating tests are next executed.
Affected versions: Spring REST Docs 4.0.0; 3.0.0 through 3.0.5; 2.0.0.RELEASE through 2.0.8.RELEASE.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.springframework.restdocs:spring-restdocs-webtestclient | ≥ 4.0.0&&< 4.0.1 | 4.0.1 |
| ☕Maven | org.springframework.restdocs:spring-restdocs-webtestclient | ≥ 3.0.0&&< 3.0.6 | 3.0.6 |
| ☕Maven | org.springframework.restdocs:spring-restdocs-webtestclient | all versions | No fix |
| ☕Maven | org.springframework.restdocs:spring-restdocs-restassured | ≥ 4.0.0&&< 4.0.1 | 4.0.1 |
| ☕Maven | org.springframework.restdocs:spring-restdocs-restassured | ≥ 3.0.0&&< 3.0.6 | 3.0.6 |
| ☕Maven | org.springframework.restdocs:spring-restdocs-restassured | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.springframework.restdocs:spring-restdocs-webtestclient. 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 org.springframework.restdocs:spring-restdocs-webtestclient to 4.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-40991 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 CVE-2026-40991 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 CVE-2026-40991. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-40991 in your dependencies?
O3 detects CVE-2026-40991 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.