Fragnesia Linux kernel local privilege escalation vulnerability mitigations

A local privilege escalation (LPE) vulnerability called 'Fragnesia' was publicly disclosed on May 13, 2026, affecting the Linux kernel across all Ubuntu releases (14.04 through 26.04 LTS). It targets ESP (Encapsulating Security Protocol) kernel modules used by IPsec, the same modules affected by the earlier Dirty Frag vulnerability. Canonical rates it CVSS 3.1 score 7.8 (HIGH). Beyond host privilege escalation, it may also enable container escape in container deployments. Step-by-step mitigation instructions are provided: blocking esp4/esp6 kernel modules via modprobe configuration, regenerating initramfs, and unloading the modules. Systems that already applied Dirty Frag mitigations are already protected. The mitigation may impact IPsec/VPN deployments using tools like StrongSwan.