CVE-2025-38255lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly()
- 5.5MediumCVSS base score
- 0.17%Exploitation in 30 daysEPSS · top 94% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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. [[email protected]: also fix the non-SMP version]
Timeline
ID reserved
By Linux
- 3 months later
· 3 months later
Published
- 16 months later
· 16 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Analyzed | 3.1 | Medium5.5 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.17% · top 94% of all CVEs (15 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.
Affected products
- affected 6a6dcae8f486c3f3298d0767d34505121c7b0b81 – < 64a99eff8dcf1f951a544e6058341b2b19a8fdbd
- affected 6a6dcae8f486c3f3298d0767d34505121c7b0b81 – < 29d39e0d5f16c060e32542b2cf351c09fd22b250
- affected 6a6dcae8f486c3f3298d0767d34505121c7b0b81 – < 911ef2e8a7de5b2bae8ff11fb0bd01f699e6db65
- affected 6a6dcae8f486c3f3298d0767d34505121c7b0b81 – < df831e97739405ecbaddb85516bc7d4d1c933d6b
- affected 6.3
- unaffected < 6.3
- unaffected 6.6.96 – ≤ 6.6.*
- unaffected 6.12.36 – ≤ 6.12.*
- unaffected 6.15.5 – ≤ 6.15.*
- unaffected 6.16 – ≤ *
References
References4
- https://git.kernel.org/stable/c/64a99eff8dcf1f951a544e6058341b2b19a8fdbd (opens in a new tab)
- https://git.kernel.org/stable/c/29d39e0d5f16c060e32542b2cf351c09fd22b250 (opens in a new tab)
- https://git.kernel.org/stable/c/911ef2e8a7de5b2bae8ff11fb0bd01f699e6db65 (opens in a new tab)
- https://git.kernel.org/stable/c/df831e97739405ecbaddb85516bc7d4d1c933d6b (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2025-20806 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2025-38255)Record last updated .