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Linux Kernel CVE-2026-53040

| EUVDEUVD-2026-38908 HIGH
Use After Free (CWE-416)
2026-06-24 Linux GHSA-4j7p-pwp5-4v56
Buffer Overflow Linux Use After Free Memory Corruption Red Hat Suse
7.1
CVSS 3.1 · Vendor: Linux
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Severity by source

Vendor (Linux) PRIMARY
7.1 HIGH
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
vuln.today AI
7.1 HIGH

Local trigger via ioctl on a mounted crafted image (AV:L, PR:L, AC:L); OOB read leaks kernel memory (C:H) and can panic (A:H); no integrity impact and no scope change.

3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
4.0 AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE
6.2 MEDIUM
AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Primary rating from Vendor (Linux).

CVSS VectorVendor: Linux

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

Lifecycle Timeline

5
Analysis Generated
Jun 28, 2026 - 08:54 vuln.today
CVSS changed
Jun 28, 2026 - 08:22 NVD
7.1 (HIGH)
Patch available
Jun 24, 2026 - 18:02 EUVD
CVE Published
Jun 24, 2026 - 16:29 cve.org
HIGH 7.1
CVE Published
Jun 24, 2026 - 16:29 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

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.

AnalysisAI

Out-of-bounds memory read in the Linux kernel's OCFS2 filesystem driver allows a local user to leak kernel memory or crash the system by issuing the OCFS2_IOC_INFO ioctl with the OCFS2_INFO_FL_NON_COHERENT flag against a crafted or malicious OCFS2 image. The non-coherent freefrag scan path trusts the on-disk bg_bits group-descriptor field as a bitmap limit without validation, driving the bitmap walk past the end of the block buffer. No public exploit identified at time of analysis, and EPSS is low (0.18%, 7th percentile), consistent with a local, filesystem-mount-dependent kernel bug rather than a remotely scanned threat.

Technical ContextAI

OCFS2 (Oracle Cluster File System v2) is a shared-disk cluster filesystem in the mainline Linux kernel. Free-space fragmentation reporting via the OCFS2_IOC_INFO ioctl walks allocator group descriptors and tests their allocation bitmaps. There are two code paths: the coherent path reads group descriptors through ocfs2_read_group_descriptor(), which validates the descriptor before use, while the non-coherent path (OCFS2_INFO_FL_NON_COHERENT) uses ocfs2_read_blocks_sync() and skips that validation. In ocfs2_info_freefrag_scan_chain() (fs/ocfs2/ioctl.c) the on-disk bg_bits field is used directly as the bitmap scan limit, so an impossible bg_bits value walks test_bit_le past the end of the allocated block. The root cause is a missing bounds/consistency check on attacker-controlled on-disk metadata (an out-of-bounds read / improper validation class; the input tags it as Buffer Overflow, though it is read-side). CPE coverage is cpe:2.3:a:linux:linux, i.e. the upstream Linux kernel. CWE was not assigned (N/A) in the source data.

RemediationAI

Apply the vendor-released patch by upgrading to a fixed kernel for your branch: 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33, 7.0.10, or mainline 7.1 or later (the fix adds ocfs2_group_bitmap_size() validation, rejects descriptors whose bg_bits exceeds capacity, and clamps the scan). The corresponding stable commits are at git.kernel.org (e.g. https://git.kernel.org/stable/c/3e167e230d19cd273108bab2e4c61800fc335ae8) and the advisory is https://nvd.nist.gov/vuln/detail/CVE-2026-53040. Where immediate patching is not possible, the practical compensating controls are: do not mount untrusted or attacker-supplied OCFS2 images, and disable automatic mounting of removable/external filesystems (trade-off: breaks convenience auto-mount workflows); restrict the CAP_SYS_ADMIN/mount capability so unprivileged users cannot mount filesystems (trade-off: may affect containers or user-mount tooling); and if OCFS2 is not required, blacklist the ocfs2 kernel module to eliminate the attack surface entirely (trade-off: unavailable only where OCFS2 is actually used).

Same weakness CWE-416 – Use After Free

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Same technique Buffer Overflow

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CVE-2019-11043 CRITICAL POC
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CVE-2009-0927 HIGH POC
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CVE-2012-1889 HIGH POC
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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
Container suse/sl-micro/6.0/base-os-container:2.1.3-7.168 Container suse/sl-micro/6.1/base-os-container:2.2.1-5.149 Affected
Container suse/sl-micro/6.0/rt-os-container:2.1.3-7.197 Container suse/sl-micro/6.1/rt-os-container:2.2.1-5.145 Affected
Image SLES15-SP7-Azure-3P Image SLES15-SP7-Azure-Basic Image SLES15-SP7-Azure-Standard Image SLES15-SP7-HPC-Azure Affected
Image SLES15-SP7-BYOS-Azure Image SLES15-SP7-BYOS-GCE Image SLES15-SP7-CHOST-BYOS-Aliyun Image SLES15-SP7-CHOST-BYOS-Azure Image SLES15-SP7-CHOST-BYOS-EC2 Image SLES15-SP7-CHOST-BYOS-GCE Image SLES15-SP7-CHOST-BYOS-GDC Image SLES15-SP7-CHOST-BYOS-SAP-CCloud Image SLES15-SP7-EC2 Image SLES15-SP7-EC2-ECS-HVM Image SLES15-SP7-GCE Image SLES15-SP7-HPC-BYOS-Azure Image SLES15-SP7-HPC-BYOS-EC2 Image SLES15-SP7-HPC-BYOS-GCE Image SLES15-SP7-Hardened-BYOS-Azure Image SLES15-SP7-Hardened-BYOS-EC2 Image SLES15-SP7-Hardened-BYOS-GCE Image SLES15-SP7-SAPCAL-Azure Image SLES15-SP7-SAPCAL-EC2 Image SLES15-SP7-SAPCAL-GCE Affected
Image SLES15-SP7-SAP-Azure Image SLES15-SP7-SAP-Azure-3P Image SLES15-SP7-SAP-BYOS-Azure Image SLES15-SP7-SAP-BYOS-EC2 Image SLES15-SP7-SAP-BYOS-GCE Image SLES15-SP7-SAP-EC2 Image SLES15-SP7-SAP-GCE Image SLES15-SP7-SAP-Hardened-Azure Image SLES15-SP7-SAP-Hardened-BYOS-Azure Image SLES15-SP7-SAP-Hardened-BYOS-EC2 Image SLES15-SP7-SAP-Hardened-BYOS-GCE Image SLES15-SP7-SAP-Hardened-GCE Affected

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CVE-2026-53040 vulnerability details – vuln.today
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