Linux: Use After Free
CVE-2026-53040 is a high-severity use after free 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 bb2906a1065ec28de021bac2ed03f2624edd7d07, 3e167e230d19cd273108bab2e4c61800fc335ae8, 0998674eec138c55e9e349b9cbd9dbc5129a9cc8 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 0.12% 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 bb2906a1065ec28de021bac2ed03f2624edd7d07 or 3e167e230d19cd273108bab2e4c61800fc335ae8 or 0998674eec138c55e9e349b9cbd9dbc5129a9cc8 or bb3c54d1e71578521111f1a1ee7d5f4761a242b8, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.258 or 5.15.209 or 6.1.175 or 6.6.141, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | d24a10b9f8ed548981696cd36e2b4f16e6f360b1 up to, but not including, bb2906a1065ec28de021bac2ed03f2624edd7d07; d24a10b9f8ed548981696cd36e2b4f16e6f360b1 up to, but not including, 3e167e230d19cd273108bab2e4c61800fc335ae8; d24a10b9f8ed548981696cd36e2b4f16e6f360b1 up to, but not including, 0998674eec138c55e9e349b9cbd9dbc5129a9cc8; d24a10b9f8ed548981696cd36e2b4f16e6f360b1 up to, but not including, bb3c54d1e71578521111f1a1ee7d5f4761a242b8; d24a10b9f8ed548981696cd36e2b4f16e6f360b1 up to, but not including, 05d0cbea41167b6b061c6ba5b70ee5a9a7a24c9e; d24a10b9f8ed548981696cd36e2b4f16e6f360b1 up to, but not including, 4c2d62ddde8928db12f4608950b67a20e67deab2; d24a10b9f8ed548981696cd36e2b4f16e6f360b1 up to, but not including, e0dcf12665d6dde37facf790803cdad44d5c328c; d24a10b9f8ed548981696cd36e2b4f16e6f360b1 up to, but not including, 8f687eeed3da3012152b0f9473f578869de0cd7b; and 1 more ranges | bb2906a1065ec28de021bac2ed03f2624edd7d07, 3e167e230d19cd273108bab2e4c61800fc335ae8, 0998674eec138c55e9e349b9cbd9dbc5129a9cc8, bb3c54d1e71578521111f1a1ee7d5f4761a242b8, 05d0cbea41167b6b061c6ba5b70ee5a9a7a24c9e, 4c2d62ddde8928db12f4608950b67a20e67deab2 |
| Linux | Linux Kernel | 3.0 up to, but not including, 5.10.258; 5.11 up to, but not including, 5.15.209; 5.16 up to, but not including, 6.1.175; 6.2 up to, but not including, 6.6.141; 6.7 up to, but not including, 6.12.91; 6.13 up to, but not including, 6.18.33; 6.19 up to, but not including, 7.0.10 | 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33 |
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 CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: ocfs2: validate bg_bits during freefrag scan [BUG] A crafted filesystem can trigger an out-of-bounds bitmap walk when OCFS2_IOC_INFO is issued with OCFS2_INFO_FL_NON_COHERENT. BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline] BUG: KASAN: use-after-free in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] BUG: KASAN: use-after-free in test_bit_le include/asm-generic/bitops/le.h:21 [inline] BUG: KASAN: use-after-free in ocfs2_info_freefrag_scan_chain fs/ocfs2/ioctl.c:495 [inline] BUG: KASAN: use-after-free in ocfs2_info_freefrag_scan_bitmap fs/ocfs2/ioctl.c:588 [inline] BUG: KASAN: use-after-free in ocfs2_info_handle_freefrag fs/ocfs2/ioctl.c:662 [inline] BUG: KASAN: use-after-free in ocfs2_info_handle_request+0x1c66/0x3370 fs/ocfs2/ioctl.c:754 Read of size 8 at addr ffff888031bce000 by task syz.0.636/1435 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0xbe/0x130 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xd1/0x650 mm/kasan/report.c:482 kasan_report+0xfb/0x140 mm/kasan/report.c:595 check_region_inline mm/kasan/generic.c:186 [inline] kasan_check_range+0x11c/0x200 mm/kasan/generic.c:200 __kasan_check_read+0x11/0x20 mm/kasan/shadow.c:31 instrument_atomic_read include/linux/instrumented.h:68 [inline] _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] test_bit_le include/asm-generic/bitops/le.h:21 [inline] ocfs2_info_freefrag_scan_chain fs/ocfs2/ioctl.c:495 [inline] ocfs2_info_freefrag_scan_bitmap fs/ocfs2/ioctl.c:588 [inline] ocfs2_info_handle_freefrag fs/ocfs2/ioctl.c:662 [inline] ocfs2_info_handle_request+0x1c66/0x3370 fs/ocfs2/ioctl.c:754 ocfs2_info_handle+0x18d/0x2a0 fs/ocfs2/ioctl.c:828 ocfs2_ioctl+0x632/0x6e0 fs/ocfs2/ioctl.c:913 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x197/0x1e0 fs/ioctl.c:583 ... [CAUSE] ocfs2_info_freefrag_scan_chain() uses on-disk bg_bits directly as the bitmap scan limit. The coherent path reads group descriptors through ocfs2_read_group_descriptor(), which validates the descriptor before use. The non-coherent path uses ocfs2_read_blocks_sync() instead and skips that validation, so an impossible bg_bits value can drive the bitmap walk past the end of the block. [FIX] Compute the bitmap capacity from the filesystem format with ocfs2_group_bitmap_size(), report descriptors whose bg_bits exceeds that limit, and clamp the scan to the computed capacity. This keeps the freefrag report going while avoiding reads beyond the buffer.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/05d0cbea41167b6b061c6ba5b70ee5a9a7a24c9e
- git.kernel.org/stable/c/0998674eec138c55e9e349b9cbd9dbc5129a9cc8
- git.kernel.org/stable/c/3e167e230d19cd273108bab2e4c61800fc335ae8
- git.kernel.org/stable/c/4c2d62ddde8928db12f4608950b67a20e67deab2
- git.kernel.org/stable/c/8f687eeed3da3012152b0f9473f578869de0cd7b
- git.kernel.org/stable/c/bb2906a1065ec28de021bac2ed03f2624edd7d07
- git.kernel.org/stable/c/bb3c54d1e71578521111f1a1ee7d5f4761a242b8
- git.kernel.org/stable/c/e0dcf12665d6dde37facf790803cdad44d5c328c
Recent Use After Free vulnerabilities
- 7.5 High severity
- 8.8 High severity
- 7.8 High severity
- 8.8 High severity
- 8.8 High severity
- 9.6 Critical severity
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