CVE-2025-38255: Linux kernel · lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly()
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in df831e97739405ecbaddb85516bc7d4d1c933d6b : update Linux kernel when convenient.
Data as of 5 Nov 2026, 21:19 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
Thin evidence
One scorer or none- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-11-05.
- Patch
- Available – fixed in df831e97739405ecbaddb85516bc7d4d1c933d6b, 911ef2e8a7de5b2bae8ff11fb0bd01f699e6db65, 64a99eff8dcf1f951a544e6058341b2b19a8fdbd +1
Exploitation evidence
Disclosed: evidence found.
CVE published 9 Jul 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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 5 Nov 2026.
What to do
Upgrade Linux kernel to df831e97739405ecbaddb85516bc7d4d1c933d6b, 911ef2e8a7de5b2bae8ff11fb0bd01f699e6db65, 64a99eff8dcf1f951a544e6058341b2b19a8fdbd or 29d39e0d5f16c060e32542b2cf351c09fd22b250.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in– |
Description
In the Linux kernel, the following vulnerability has been resolved: lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly() While testing null_blk with configfs, echo 0 > poll_queues will trigger following panic: BUG: kernel NULL pointer dereference, address: 0000000000000010 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 27 UID: 0 PID: 920 Comm: bash Not tainted 6.15.0-02023-gadbdb95c8696-dirty #1238 PREEMPT(undef) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:__bitmap_or+0x48/0x70 Call Trace: <TASK> __group_cpus_evenly+0x822/0x8c0 group_cpus_evenly+0x2d9/0x490 blk_mq_map_queues+0x1e/0x110 null_map_queues+0xc9/0x170 [null_blk] blk_mq_update_queue_map+0xdb/0x160 blk_mq_update_nr_hw_queues+0x22b/0x560 nullb_update_nr_hw_queues+0x71/0xf0 [null_blk] nullb_device_poll_queues_store+0xa4/0x130 [null_blk] configfs_write_iter+0x109/0x1d0 vfs_write+0x26e/0x6f0 ksys_write+0x79/0x180 __x64_sys_write+0x1d/0x30 x64_sys_call+0x45c4/0x45f0 do_syscall_64+0xa5/0x240 entry_SYSCALL_64_after_hwframe+0x76/0x7e Root cause is that numgrps is set to 0, and ZERO_SIZE_PTR is returned from kcalloc(), and later ZERO_SIZE_PTR will be deferenced. Fix the problem by checking numgrps first in group_cpus_evenly(), and return NULL directly if numgrps is zero. [yukuai3@huawei.com: also fix the non-SMP version]
References
- git.kernel.org/stable/c/64a99eff8dcf1f951a544e6058341b2b19a8fdbd (opens in a new tab)
- git.kernel.org/stable/c/29d39e0d5f16c060e32542b2cf351c09fd22b250 (opens in a new tab)
- git.kernel.org/stable/c/911ef2e8a7de5b2bae8ff11fb0bd01f699e6db65 (opens in a new tab)
- git.kernel.org/stable/c/df831e97739405ecbaddb85516bc7d4d1c933d6b (opens in a new tab)