CVE-2025-21631

Public on

Last Modified: UTC

Moderate Moderate Impact What does this mean?
6 CVSS v3 Base Score

Description

The MITRE CVE dictionary describes this issue as

In the Linux kernel, the following vulnerability has been resolved: block, bfq: fix waker_bfqq UAF after bfq_split_bfqq() Our syzkaller report a following UAF for v6.6: BUG: KASAN: slab-use-after-free in bfq_init_rq+0x175d/0x17a0 block/bfq-iosched.c:6958 Read of size 8 at addr ffff8881b57147d8 by task fsstress/232726 CPU: 2 PID: 232726 Comm: fsstress Not tainted 6.6.0-g3629d1885222 #39 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x91/0xf0 lib/dump_stack.c:106 print_address_description.constprop.0+0x66/0x300 mm/kasan/report.c:364 print_report+0x3e/0x70 mm/kasan/report.c:475 kasan_report+0xb8/0xf0 mm/kasan/report.c:588 hlist_add_head include/linux/list.h:1023 [inline] bfq_init_rq+0x175d/0x17a0 block/bfq-iosched.c:6958 bfq_insert_request.isra.0+0xe8/0xa20 block/bfq-iosched.c:6271 bfq_insert_requests+0x27f/0x390 block/bfq-iosched.c:6323 blk_mq_insert_request+0x290/0x8f0 block/blk-mq.c:2660 blk_mq_submit_bio+0x1021/0x15e0 block/blk-mq.c:3143 __submit_bio+0xa0/0x6b0 block/blk-core.c:639 __submit_bio_noacct_mq block/blk-core.c:718 [inline] submit_bio_noacct_nocheck+0x5b7/0x810 block/blk-core.c:747 submit_bio_noacct+0xca0/0x1990 block/blk-core.c:847 __ext4_read_bh fs/ext4/super.c:205 [inline] ext4_read_bh+0x15e/0x2e0 fs/ext4/super.c:230 __read_extent_tree_block+0x304/0x6f0 fs/ext4/extents.c:567 ext4_find_extent+0x479/0xd20 fs/ext4/extents.c:947 ext4_ext_map_blocks+0x1a3/0x2680 fs/ext4/extents.c:4182 ext4_map_blocks+0x929/0x15a0 fs/ext4/inode.c:660 ext4_iomap_begin_report+0x298/0x480 fs/ext4/inode.c:3569 iomap_iter+0x3dd/0x1010 fs/iomap/iter.c:91 iomap_fiemap+0x1f4/0x360 fs/iomap/fiemap.c:80 ext4_fiemap+0x181/0x210 fs/ext4/extents.c:5051 ioctl_fiemap.isra.0+0x1b4/0x290 fs/ioctl.c:220 do_vfs_ioctl+0x31c/0x11a0 fs/ioctl.c:811 __do_sys_ioctl fs/ioctl.c:869 [inline] __se_sys_ioctl+0xae/0x190 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x70/0x120 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x78/0xe2 Allocated by task 232719: kasan_save_stack+0x22/0x50 mm/kasan/common.c:45 kasan_set_track+0x25/0x30 mm/kasan/common.c:52 __kasan_slab_alloc+0x87/0x90 mm/kasan/common.c:328 kasan_slab_alloc include/linux/kasan.h:188 [inline] slab_post_alloc_hook mm/slab.h:768 [inline] slab_alloc_node mm/slub.c:3492 [inline] kmem_cache_alloc_node+0x1b8/0x6f0 mm/slub.c:3537 bfq_get_queue+0x215/0x1f00 block/bfq-iosched.c:5869 bfq_get_bfqq_handle_split+0x167/0x5f0 block/bfq-iosched.c:6776 bfq_init_rq+0x13a4/0x17a0 block/bfq-iosched.c:6938 bfq_insert_request.isra.0+0xe8/0xa20 block/bfq-iosched.c:6271 bfq_insert_requests+0x27f/0x390 block/bfq-iosched.c:6323 blk_mq_insert_request+0x290/0x8f0 block/blk-mq.c:2660 blk_mq_submit_bio+0x1021/0x15e0 block/blk-mq.c:3143 __submit_bio+0xa0/0x6b0 block/blk-core.c:639 __submit_bio_noacct_mq block/blk-core.c:718 [inline] submit_bio_noacct_nocheck+0x5b7/0x810 block/blk-core.c:747 submit_bio_noacct+0xca0/0x1990 block/blk-core.c:847 __ext4_read_bh fs/ext4/super.c:205 [inline] ext4_read_bh_nowait+0x15a/0x240 fs/ext4/super.c:217 ext4_read_bh_lock+0xac/0xd0 fs/ext4/super.c:242 ext4_bread_batch+0x268/0x500 fs/ext4/inode.c:958 __ext4_find_entry+0x448/0x10f0 fs/ext4/namei.c:1671 ext4_lookup_entry fs/ext4/namei.c:1774 [inline] ext4_lookup.part.0+0x359/0x6f0 fs/ext4/namei.c:1842 ext4_lookup+0x72/0x90 fs/ext4/namei.c:1839 __lookup_slow+0x257/0x480 fs/namei.c:1696 lookup_slow fs/namei.c:1713 [inline] walk_component+0x454/0x5c0 fs/namei.c:2004 link_path_walk.part.0+0x773/0xda0 fs/namei.c:2331 link_path_walk fs/namei.c:3826 [inline] path_openat+0x1b9/0x520 fs/namei.c:3826 do_filp_open+0x1b7/0x400 fs/namei.c:3857 do_sys_openat2+0x5dc/0x6e0 fs/open.c:1428 do_sys_open fs/open.c:1443 [inline] __do_sys_openat fs/open.c:1459 [inline] __se_sys_openat fs/open.c:1454 [inline] __x64_sys_openat+0x148/0x200 fs/open.c:1454 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_6 ---truncated---

Additional Information

External References

Content from www.cve.org is not included.https://www.cve.org/CVERecord?id=CVE-2025-21631

Content from nvd.nist.gov is not included.https://nvd.nist.gov/vuln/detail/CVE-2025-21631

Content from lore.kernel.org is not included.https://lore.kernel.org/linux-cve-announce/2025011939-CVE-2025-21631-5f2d@gregkh/T

Affected Packages and Issued Red Hat Security Errata

Products / Services Components State Errata
Red Hat Enterprise Linux 10 kernel Affected
Red Hat Enterprise Linux 6 kernel Not affected
Red Hat Enterprise Linux 7 kernel Not affected
Red Hat Enterprise Linux 7 kernel-rt Not affected
Red Hat Enterprise Linux 8 kernel Not affected
Red Hat Enterprise Linux 8 kernel-rt Not affected
Red Hat Enterprise Linux 9 kernel-rt Affected
Red Hat Enterprise Linux 9 kernel Fixed RHSA-2025:20518
Unless explicitly stated as not affected, all previous versions of packages in any minor update stream of a product listed here should be assumed vulnerable, although may not have been subject to full analysis.

Common Vulnerability Scoring System (CVSS) Score Details

Important note

CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authorities (CNA) source for its products and services (see Red Hat classifications ).

CVSS v3 Score Breakdown Red Hat NVD
CVSS v3 Base Score 6 7.8
Attack Vector Local Local
Attack Complexity Low Low
Privileges Required High Low
User Interaction None None
Scope Unchanged Unchanged
Confidentiality Impact High High
Integrity Impact None High
Availability Impact High High

CVSS v3 Vector

Red Hat CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:H

NVD CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

 For open source software shipped by multiple vendors, the CVSS base scores may vary for each vendor's version depending on the version they ship, how they ship it, the platform, and even how the software is compiled. This makes scoring of vulnerabilities difficult for third-party vulnerability databases such as NVD that only provide a single CVSS base score for each vulnerability. Red Hat scores reflect how a vulnerability affects our products specifically.

For more information, see https://access.redhat.com/solutions/762393.

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?
  • "Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.
  • "Affected" means that our Analysis Team has determined that this product is affected by this vulnerability and might release a fix to address this in the near future.

What can I do if my product is listed as "Will not fix"?

 A "will not fix" status means that a fix for an affected product version is not planned or not possible due to complexity, which may create additional risk.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Upgrade to a supported product version that includes a fix for this vulnerability (recommended).
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.

What can I do if my product is listed as "Fix deferred"?

 A deferred status means that a fix for an affected product version is not guaranteed due to higher-priority development work.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.
  • Red Hat Engineering focuses on addressing high-priority issues based on their complexity or limited lifecycle support. Therefore, lower-priority issues will not receive immediate fixes.

What is a mitigation?

 A mitigation is an action that can be taken to reduce the impact of a security vulnerability, without deploying any fixes.

I have a Red Hat product but it is not in the above list, is it affected?

 The listed products were found to include one or more of the components that this vulnerability affects. These products underwent a thorough evaluation to determine their affectedness by this vulnerability. Note that layered products (such as container-based offerings) that consume affected components from any of the products listed in this table may be affected and are not represented.

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

 In order to maintain code stability and compatibility, Red Hat usually does not rebase packages to entirely new versions. Instead, we backport fixes and new features to an older version of the package we distribute. This can result in some security scanners that only consider the package version to report the package as vulnerable. To avoid this, we suggest that you use an approved vulnerability scanner from our This content is not included.Red Hat Vulnerability Scanner Certification program.

My product is listed as "Out of Support Scope". What does this mean?

 When a product is listed as "Out of Support Scope", it means a vulnerability with the impact level assigned to this CVE is no longer covered by its current support lifecycle phase. The product has been identified to contain the impacted component, but analysis to determine whether it is affected or not by this vulnerability was not performed. The product should be assumed to be affected. Customers are advised to apply any mitigation options documented on this page, consider removing or disabling the impacted component, or upgrade to a supported version of the product that has an update available.