GHSA-c35g-jr5f-h83p is a medium-severity (CVSS 5.9) Improper Input Validation vulnerability in slixmpp. 3 public exploit references exist, so weaponization risk is real. A fix is available for slixmpp — see the affected versions and patch details below.
SleekXMPP and Slixmpp Incorrect Implementation of Message Carbons
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-c35g-jr5f-h83p 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
slixmpp🐍sleekxmppReal-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
An incorrect implementation of "XEP-0280: Message Carbons" in multiple XMPP clients allows a remote attacker to impersonate any user, including contacts, in the vulnerable application's display. This allows for various kinds of social engineering attacks. This CVE is for SleekXMPP up to 1.3.1 and Slixmpp all versions up to 1.2.3, as bundled in poezio (0.8 - 0.10) and other products.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | slixmpp | all versions | 1.2.4pip install --upgrade 'slixmpp==1.2.4' |
| 🐍PyPI | sleekxmpp | all versions | 1.3.2pip install --upgrade 'sleekxmpp==1.3.2' |
Research 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 slixmpp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update slixmpp to 1.2.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-c35g-jr5f-h83p 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-c35g-jr5f-h83p can be triaged on real exposure rather than presence alone.
Tailored to GHSA-c35g-jr5f-h83p. 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-c35g-jr5f-h83p in your dependencies?
O3 Security finds GHSA-c35g-jr5f-h83p across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.