CVE-2019-1000021 is a high-severity (CVSS 7.5) vulnerability in slixmpp. 1 public exploit reference exists, so weaponization risk is real. A fix is available for slixmpp — see the affected versions and patch details below.
slixmpp Incorrect Access Control
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-2019-1000021 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
slixmppReal-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
slixmpp version before commit 7cd73b594e8122dddf847953fcfc85ab4d316416 contains an incorrect Access Control vulnerability in XEP-0223 plugin (Persistent Storage of Private Data via PubSub) options profile, used for the configuration of default access model that can result in all of the contacts of the victim can see private data having been published to a PEP node. This attack appears to be exploitable if the user of this library publishes any private data on PEP, the node isn't configured to be private. This vulnerability appears to have been fixed in commit 7cd73b594e8122dddf847953fcfc85ab4d316416 which is included in slixmpp 1.4.2.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | slixmpp | all versions | 1.4.2pip install --upgrade 'slixmpp==1.4.2' |
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 1.4.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-1000021 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-2019-1000021 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2019-1000021. 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-2019-1000021 in your dependencies?
O3 Security finds CVE-2019-1000021 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.