GHSA-vv2x-vrpj-qqpq is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in bleach. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for bleach — see the affected versions and patch details below.
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for GHSA-vv2x-vrpj-qqpq.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
bleachReal-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
Impact
A mutation XSS affects users calling bleach.clean with all of:
svgormathin the allowed tagsporbrin allowed tagsstyle,title,noscript,script,textarea,noframes,iframe, orxmpin allowed tags- the keyword argument
strip_comments=False
Note: none of the above tags are in the default allowed tags and strip_comments defaults to True.
Patches
Users are encouraged to upgrade to bleach v3.3.0 or greater.
Note: bleach v3.3.0 introduces a breaking change to escape HTML comments by default.
Workarounds
-
modify
bleach.cleancalls to at least one of:- not allow the
style,title,noscript,script,textarea,noframes,iframe, orxmptag - not allow
svgormathtags - not allow
porbrtags - set
strip_comments=True
- not allow the
-
A strong Content-Security-Policy without
unsafe-inlineandunsafe-evalscript-srcs) will also help mitigate the risk.
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1689399
- https://advisory.checkmarx.net/advisory/CX-2021-4303
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23980
- https://cure53.de/fp170.pdf
Credits
- Reported by Yaniv Nizry from the CxSCA AppSec group at Checkmarx
- Additional eject tags not mentioned in the original advisory and the CSP mitigation line being truncated in the revised advisory reported by Michał Bentkowski at Securitum
For more information
If you have any questions or comments about this advisory:
- Open an issue at https://github.com/mozilla/bleach/issues
- Email us at [email protected]
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | bleach | all versions | 3.3.0pip install --upgrade 'bleach==3.3.0' |
Affected Products
bleachmozillaResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for bleach, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update bleach to 3.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vv2x-vrpj-qqpq is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Automation Hub 4.2 for RHEL 7 | automation-hub-0:4.2.2-1.el7pc | RHSA-2021:0781 |
Frequently Asked Questions
Is GHSA-vv2x-vrpj-qqpq in your dependencies?
Find it across PyPI, including transitive dependencies.