CVE-2023-38700 is a low-severity (CVSS 3.5) Information Exposure vulnerability in matrix-appservice-irc. A fix is available for matrix-appservice-irc — see the affected versions and patch details below.
matrix-appservice-irc events can be crafted to leak parts of targeted messages from other bridged rooms
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-2023-38700.
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
CVE-2023-38700 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 378,567 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.
matrix-appservice-ircnpmDescription
Impact
It was possible to craft an event such that it would leak part of a targeted message event from another bridged room. This required knowing an event ID to target.
Patches
Please upgrade to 1.0.1.
Workarounds
You can set the matrixHandler.eventCacheSize config value to 0 to workaround this bug. However, this may impact performance.
Credits
Discovered and reported by Val Lorentz.
For more information
If you have any questions or comments about this advisory email us at [email protected].
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | matrix-appservice-irc | all versions | 1.0.1npm install matrix-appservice-irc@1.0.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for matrix-appservice-irc, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update matrix-appservice-irc to 1.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-38700 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 CVE-2023-38700 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-38700. 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-2023-38700 in your dependencies?
O3 Security finds CVE-2023-38700 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.