GHSA-3wc5-fcw2-2329 is a medium-severity (CVSS 5.5) CWE-184 vulnerability in katex. A fix is available for katex — see the affected versions and patch details below.
KaTeX missing normalization of the protocol in URLs allows bypassing forbidden protocols
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-3wc5-fcw2-2329.
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-3wc5-fcw2-2329 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 377,166 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
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
katexnpmDescription
Impact
Code that uses KaTeX's trust option, specifically that provides a function to block-list certain URL protocols, can be fooled by URLs in malicious inputs that use uppercase characters in the protocol. In particular, this can allow for malicious input to generate javascript: links in the output, even if the trust function tries to forbid this protocol via trust: (context) => context.protocol !== 'javascript'.
Patches
Upgrade to KaTeX v0.16.10 to remove this vulnerability.
Workarounds
- Allow-list instead of block protocols in your
trustfunction. - Manually lowercase
context.protocolviacontext.protocol.toLowerCase()before attempting to check for certain protocols. - Avoid use of or turn off the
trustoption.
Details
KaTeX did not normalize the protocol entry of the context object provided to a user-specified trust-function, so it could be a mix of lowercase and/or uppercase letters.
It is generally better to allow-list by protocol, in which case this would normally not be an issue. But in some cases, you might want to block-list, and the KaTeX documentation even provides such an example:
Allow all commands but forbid specific protocol:
trust: (context) => context.protocol !== 'file'
Currently KaTeX internally sees file: and File: URLs as different protocols, so context.protocol can be file or File, so the above check does not suffice. A simple workaround would be:
trust: (context) => context.protocol.toLowerCase() !== 'file'
Most URL parsers normalize the scheme to lowercase. For example, RFC3986 says:
Although schemes are case-insensitive, the canonical form is lowercase and documents that specify schemes must do so with lowercase letters. An implementation should accept uppercase letters as equivalent to lowercase in scheme names (e.g., allow "HTTP" as well as "http") for the sake of robustness but should only produce lowercase scheme names for consistency.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | katex | ≥ 0.11.0&&< 0.16.10 | 0.16.10npm install katex@0.16.10 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for katex, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update katex to 0.16.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3wc5-fcw2-2329 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-3wc5-fcw2-2329 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-3wc5-fcw2-2329. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
Frequently Asked Questions
Is GHSA-3wc5-fcw2-2329 in your dependencies?
O3 Security finds GHSA-3wc5-fcw2-2329 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.