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CVE-2026-53040— ocfs2: validate bg_bits during freefrag scan

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的操作系统Linux所使用的内核。 Linux kernel 3.0版本存在安全漏洞，该漏洞源于ocfs2文件系统在freefrag扫描过程中未验证bg_bits值，可能导致释放后重用。

CVSS 7.1 · High EPSS 0.12% · P2

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux d24a10b9f8ed548981696cd36e2b4f16e6f360b1< bb2906a1065ec28de021bac2ed03f2624edd7d07 affected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1< 3e167e230d19cd273108bab2e4c61800fc335ae8 affected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1< 0998674eec138c55e9e349b9cbd9dbc5129a9cc8 affected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1< bb3c54d1e71578521111f1a1ee7d5f4761a242b8 affected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1< 05d0cbea41167b6b061c6ba5b70ee5a9a7a24c9e affected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1< 4c2d62ddde8928db12f4608950b67a20e67deab2 affected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1< e0dcf12665d6dde37facf790803cdad44d5c328c affected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1< 8f687eeed3da3012152b0f9473f578869de0cd7b affected
… +10 more rows
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I. Basic Information for CVE-2026-53040

Vulnerability Information
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Vulnerability Title
ocfs2: validate bg_bits during freefrag scan
Source: CVE Program / CVE List V5
Vulnerability 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: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的操作系统Linux所使用的内核。 Linux kernel 3.0版本存在安全漏洞，该漏洞源于ocfs2文件系统在freefrag扫描过程中未验证bg_bits值，可能导致释放后重用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux d24a10b9f8ed548981696cd36e2b4f16e6f360b1 ~ bb2906a1065ec28de021bac2ed03f2624edd7d07 -
Linux Linux 3.0 -

II. Public POCs for CVE-2026-53040

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III. Intelligence Information for CVE-2026-53040

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Patches & Fixes for CVE-2026-53040 (8)

Same Patch Batch · Linux · 2026-06-24 · 219 CVEs total

CVE-2026-53049 9.8 CRITICAL gfs2: add some missing log locking
CVE-2026-52993 9.8 CRITICAL tipc: fix double-free in tipc_buf_append()
CVE-2026-52989 9.8 CRITICAL nvmet-tcp: propagate nvmet_tcp_build_pdu_iovec() errors to its callers
CVE-2026-52986 9.8 CRITICAL netfilter: nf_conntrack_sip: don't use simple_strtoul
CVE-2026-52982 9.8 CRITICAL net: usb: rtl8150: fix use-after-free in rtl8150_start_xmit()
CVE-2026-53002 9.8 CRITICAL netfilter: conntrack: remove sprintf usage
CVE-2026-53086 9.8 CRITICAL net: bcmgenet: fix racing timeout handler
CVE-2026-53045 9.8 CRITICAL memory: tegra124-emc: Fix dll_change check
CVE-2026-53006 9.8 CRITICAL ipv6: fix possible UAF in icmpv6_rcv()
CVE-2026-53046 9.8 CRITICAL ksmbd: fix use-after-free from async crypto on Qualcomm crypto engine
CVE-2026-52955 9.8 CRITICAL libceph: Fix potential out-of-bounds access in crush_decode()
CVE-2026-53010 9.8 CRITICAL ksmbd: fix use-after-free in smb2_open during durable reconnect
CVE-2026-53088 9.8 CRITICAL net: bcmgenet: fix off-by-one in bcmgenet_put_txcb
CVE-2026-52924 9.8 CRITICAL sctp: purge outqueue on stale COOKIE-ECHO handling
CVE-2026-52931 9.8 CRITICAL batman-adv: tp_meter: avoid use of uninit sender vars
CVE-2026-53055 9.8 CRITICAL crypto: hisilicon/sec2 - prevent req used-after-free for sec
CVE-2026-52914 9.8 CRITICAL batman-adv: fix fragment reassembly length accounting
CVE-2026-52958 9.1 CRITICAL libceph: Fix potential out-of-bounds access in osdmap_decode()
CVE-2026-53043 9.1 CRITICAL ocfs2/dlm: validate qr_numregions in dlm_match_regions()
CVE-2026-52999 9.1 CRITICAL netfilter: nfnetlink_osf: fix out-of-bounds read on option matching

Showing top 20 of 219 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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