A vulnerability was found in CRIU's handling of restartable sequences (rseq) during checkpoint/restore. When CRIU injects parasite code into a process for checkpointing, if the process's instruction pointer is inside an rseq critical section, the kernel redirects execution to the rseq abort handler. A malicious container process can exploit this by registering an rseq critical section with a crafted abort handler that detects and hijacks CRIU's parasite code injection.

The exploit intercepts the parasite's syscalls during checkpoint, locates and patches the parasite's dump_creds function to return spoofed credentials with full capabilities (all capability sets set to 0x1ffffffffff), zeroed UIDs/GIDs, and cleared no_new_privs/secbits. On restore, CRIU applies these spoofed credentials, granting the container process full DAC-bypass capabilities.

The attack requires that checkpoint/restore is enabled for the container runtime and that the attacker controls the code running inside the container.