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VulnerabilityPublished Updated

CVE-2025-39744: Linux kernel · rcu: Fix rcu_read_unlock() deadloop due to IRQ work

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Authoritative record:CVE-2025-39744

Not known to be exploited · CVSS 7.1 High · fixed in e7a375453cca2b8a0d2fa1b82b913f3fed7c0507 : patch Linux kernel soon.

Data as of 30 Oct 2026, 16:33 UTC

CVSS 3.1 base score
7.1High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
Patch
Available – fixed in e7a375453cca2b8a0d2fa1b82b913f3fed7c0507, ddebb2a7677673cf4438a04e1a48b8ed6b0c8e9a, b41642c87716bbd09797b1e4ea7d904f06c39b7b +3
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 11 Sep 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ 0864f057b050bc6dd68106b3185e02db5140012d, < e7a375453cca2b8a0d2fa1b82b913f3fed7c0507
Fixed in
  • e7a375453cca2b8a0d2fa1b82b913f3fed7c0507
LinuxLinuxAffected
  • ≥ 0864f057b050bc6dd68106b3185e02db5140012d, < ddebb2a7677673cf4438a04e1a48b8ed6b0c8e9a
Fixed in
  • ddebb2a7677673cf4438a04e1a48b8ed6b0c8e9a
LinuxLinuxAffected
  • ≥ 0864f057b050bc6dd68106b3185e02db5140012d, < b41642c87716bbd09797b1e4ea7d904f06c39b7b
Fixed in
  • b41642c87716bbd09797b1e4ea7d904f06c39b7b
LinuxLinuxAffected
  • ≥ 0864f057b050bc6dd68106b3185e02db5140012d, < 56c5ef194f4509df63fc0f7a91ea5973ce479b1e
Fixed in
  • 56c5ef194f4509df63fc0f7a91ea5973ce479b1e
LinuxLinuxAffected
  • ≥ 0864f057b050bc6dd68106b3185e02db5140012d, < 6b552ffd21f9be57806ade167a757f32dd66a98d
Fixed in
  • 6b552ffd21f9be57806ade167a757f32dd66a98d
LinuxLinuxAffected
  • ≥ 0864f057b050bc6dd68106b3185e02db5140012d, < 1cfa244f7198d325594e627574930b7b91df5bfe
Fixed in
  • 1cfa244f7198d325594e627574930b7b91df5bfe

Description

In the Linux kernel, the following vulnerability has been resolved: rcu: Fix rcu_read_unlock() deadloop due to IRQ work During rcu_read_unlock_special(), if this happens during irq_exit(), we can lockup if an IPI is issued. This is because the IPI itself triggers the irq_exit() path causing a recursive lock up. This is precisely what Xiongfeng found when invoking a BPF program on the trace_tick_stop() tracepoint As shown in the trace below. Fix by managing the irq_work state correctly. irq_exit() __irq_exit_rcu() /* in_hardirq() returns false after this */ preempt_count_sub(HARDIRQ_OFFSET) tick_irq_exit() tick_nohz_irq_exit() tick_nohz_stop_sched_tick() trace_tick_stop() /* a bpf prog is hooked on this trace point */ __bpf_trace_tick_stop() bpf_trace_run2() rcu_read_unlock_special() /* will send a IPI to itself */ irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu); A simple reproducer can also be obtained by doing the following in tick_irq_exit(). It will hang on boot without the patch: static inline void tick_irq_exit(void) { + rcu_read_lock(); + WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, true); + rcu_read_unlock(); + [neeraj: Apply Frederic's suggested fix for PREEMPT_RT]

References

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