CVE-2021-3914
MEDIUMCVE-2021-3914 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in redhat build of quarkus. O3 Security detects and blocks CVE-2021-3914 exploitation at runtime via eBPF exploit-chain detection and L7 egress monitoring, even on unpatched systems.
It was found that the smallrye health metrics UI component did not properly sanitize some user inputs. An attacker could use this flaw to conduct cross-site scripting attacks.
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.
Description
It was found that the smallrye health metrics UI component did not properly sanitize some user inputs. An attacker could use this flaw to conduct cross-site scripting attacks.
Affected Products
build of quarkusredhatopenshift application runtimesredhatsmallrye healthredhatDetection & mitigation playbook
Vendor / applianceDetect
Inventory every redhat build of quarkus deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for exploitation at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Fix
Apply the redhat build of quarkus security patch or hotfix for CVE-2021-3914 on the affected version, following the vendor advisory for your exact build.
Workarounds
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2021-3914 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.
Tailored to CVE-2021-3914. 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-2021-3914 being exploited in your environment?
O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2021-3914 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.