Linux: Out-of-bounds Read
CVE-2025-39744 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 7.1 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 6b552ffd21f9be57806ade167a757f32dd66a98d, e7a375453cca2b8a0d2fa1b82b913f3fed7c0507, 1cfa244f7198d325594e627574930b7b91df5bfe as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.17% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 6b552ffd21f9be57806ade167a757f32dd66a98d or e7a375453cca2b8a0d2fa1b82b913f3fed7c0507 or 1cfa244f7198d325594e627574930b7b91df5bfe or ddebb2a7677673cf4438a04e1a48b8ed6b0c8e9a, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.103 or 6.12.43 or 6.15.11 or 6.16.2, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 0864f057b050bc6dd68106b3185e02db5140012d up to, but not including, 6b552ffd21f9be57806ade167a757f32dd66a98d; 0864f057b050bc6dd68106b3185e02db5140012d up to, but not including, e7a375453cca2b8a0d2fa1b82b913f3fed7c0507; 0864f057b050bc6dd68106b3185e02db5140012d up to, but not including, 1cfa244f7198d325594e627574930b7b91df5bfe; 0864f057b050bc6dd68106b3185e02db5140012d up to, but not including, ddebb2a7677673cf4438a04e1a48b8ed6b0c8e9a; 0864f057b050bc6dd68106b3185e02db5140012d up to, but not including, 56c5ef194f4509df63fc0f7a91ea5973ce479b1e; 0864f057b050bc6dd68106b3185e02db5140012d up to, but not including, b41642c87716bbd09797b1e4ea7d904f06c39b7b; 5.3 | 6b552ffd21f9be57806ade167a757f32dd66a98d, e7a375453cca2b8a0d2fa1b82b913f3fed7c0507, 1cfa244f7198d325594e627574930b7b91df5bfe, ddebb2a7677673cf4438a04e1a48b8ed6b0c8e9a, 56c5ef194f4509df63fc0f7a91ea5973ce479b1e, b41642c87716bbd09797b1e4ea7d904f06c39b7b |
| Linux | Linux Kernel | before 6.6.103; 6.7 up to, but not including, 6.12.43; 6.13 up to, but not including, 6.15.11; 6.16 up to, but not including, 6.16.2 | 6.6.103, 6.12.43, 6.15.11, 6.16.2 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H. Scored by NVD.
Official 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]
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Read
The product reads data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that provides appropriate memory abstractions.
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/1cfa244f7198d325594e627574930b7b91df5bfe
- git.kernel.org/stable/c/56c5ef194f4509df63fc0f7a91ea5973ce479b1e
- git.kernel.org/stable/c/b41642c87716bbd09797b1e4ea7d904f06c39b7b
- git.kernel.org/stable/c/ddebb2a7677673cf4438a04e1a48b8ed6b0c8e9a
- git.kernel.org/stable/c/e7a375453cca2b8a0d2fa1b82b913f3fed7c0507
Other references
Recent Out-of-bounds Read vulnerabilities
- 7.1 High severity
- 7.1 High severity
- 7.1 High severity
- 7.1 High severity
- 7.1 High severity
- 9.1 Critical severity
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