EUVD-2026-86792
GHSA-9x8r-8wjj-jgjv
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Alert meAnalysisCVE.org
In the Linux kernel, the following vulnerability has been resolved:
reboot: fix cad_pid use-after-free race
cad_pid is a single kernel-wide struct pid pointer. proc_do_cad_pid() reads it and passes it to pid_vnr() without protecting the lifetime of the referenced struct pid. A concurrent writer can replace cad_pid and drop the final reference to the old struct pid after the reader has loaded the pointer but before pid_vnr() has finished dereferencing it, causing a use-after-free.
kill_cad_pid() has the same lifetime race when it passes cad_pid to kill_pid().
At the time this issue was reported, an unprivileged user could reach the sysctl through user and PID namespaces because cad_pid was registered in pid_table[]. Moving cad_pid back to the global reboot sysctl table corrected that namespace and permission mismatch, but did not fix the underlying lifetime race.
Fix this by treating cad_pid as an RCU-protected pointer at both read sites and by waiting for a grace period before dropping the old reference on the write side.
call_rcu(&old_pid->rcu, ...) cannot be used here because free_pid() also queues pid->rcu; queueing the same rcu_head twice can corrupt the RCU callback list.
Original KASAN crash stack: kernel/pid.c:545 pid_nr_ns()
reads freed pid->level
kernel/pid.c:556 pid_vnr()
calls pid_nr_ns()
kernel/pid.c:775 proc_do_cad_pid()
calls pid_vnr(cad_pid)
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in euvd
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Attack Technique
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
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