CVE-2021-26544 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in org.apache.livy:livy-server. A fix is available for org.apache.livy:livy-server — see the affected versions and patch details below.
Apache Livy Cross-site scripting (XSS) in session names
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-2021-26544 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 377,636 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
org.apache.livy:livy-serverReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Livy server version 0.7.0-incubating (only) is vulnerable to a cross site scripting issue in the session name. A malicious user could use this flaw to access logs and results of other users' sessions and run jobs with their privileges. This issue is fixed in Livy 0.7.1-incubating.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.livy:livy-server | ≥ 0.7.0-incubating&&< 0.7.1-incubating | 0.7.1-incubatingorg.apache.livy:livy-server:0.7.1-incubating |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.livy:livy-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.apache.livy:livy-server to 0.7.1-incubating or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-26544 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-2021-26544 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-26544. 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-2021-26544 in your dependencies?
O3 Security finds CVE-2021-26544 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.