GHSA-8v9w-p43c-r885 is a medium-severity (CVSS 6.5) Reachable Assertion vulnerability in rulex. A fix is available for rulex — see the affected versions and patch details below.
Reachable Assertion in rulex
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-8v9w-p43c-r885.
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-8v9w-p43c-r885 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 378,156 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
rulexReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Impact
When parsing untrusted rulex expressions, rulex may crash, possibly enabling a Denial of Service attack. This happens when the expression contains a multi-byte UTF-8 code point in a string literal or after a backslash, because rulex tries to slice into the code point and panics as a result.
This is a security concern for you, if
- your service parses untrusted rulex expressions (expressions provided by an untrusted user), and
- your service becomes unavailable when the thread running rulex panics.
Patches
The crashes are fixed in version 0.4.3. Affected users are advised to update to this version.
Workarounds
You can use catch_unwind to recover from panics.
For more information
If you have any questions or comments about this advisory:
- Open an issue in rulex
- Email me at [email protected]
Credits
Credit for finding these bugs goes to
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | rulex | all versions | 0.4.3cargo update -p rulex --precise 0.4.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rulex, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update rulex to 0.4.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-8v9w-p43c-r885 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-8v9w-p43c-r885 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-8v9w-p43c-r885. 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-8v9w-p43c-r885 in your dependencies?
O3 Security finds GHSA-8v9w-p43c-r885 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.