CVE-2026-11979
HIGHlibxml2 is vulnerable to multiple stack-based buffer overflows in the xmlcatalog utility when running in --shell mode. The usershell() function processes user input using fixed-size…
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
libxml2 is vulnerable to multiple stack-based buffer overflows in the xmlcatalog utility when running in --shell mode. The usershell() function processes user input using fixed-size stack buffers without proper bounds checking. By supplying an overly long input line, an attacker can overflow internal buffers (command, arg, and argv) during input parsing. This results in memory corruption within the stack frame. Successful exploitation may cause a crash or potentially allow arbitrary code execution in the context of the xmlcatalog process.
This issue has been fixed in the commit c2e233fc.
NOTE: The maintainers of this project did not agree that this issue is a vulnerability and considered it a bug.
Affected Products
libxml2xmlsoftDetection & mitigation playbook
Vendor / applianceDetect
Inventory every xmlsoft libxml2 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 remote code execution at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Remediation status
No patch has shipped for CVE-2026-11979 yet — track the xmlsoft libxml2 advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
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-2026-11979 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-2026-11979. 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-2026-11979 being exploited in your environment?
O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2026-11979 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.