EUVD-2026-38909
GHSA-gmx4-g5vq-2x9x
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Local OCFS2 access by a low-privileged user (AV:L/PR:L), no interaction; oversized copy_to_user yields kernel memory disclosure (C:H) and panic (A:H) with no integrity impact.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
ocfs2: fix listxattr handling when the buffer is full
[BUG] If an OCFS2 inode has both inline and block-based xattrs, listxattr() can return a size larger than the caller's buffer when the inline names consume that buffer exactly.
kernel BUG at mm/usercopy.c:102! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI RIP: 0010:usercopy_abort+0xb7/0xd0 mm/usercopy.c:102 Call Trace: __check_heap_object+0xe3/0x120 mm/slub.c:8243 check_heap_object mm/usercopy.c:196 [inline] __check_object_size mm/usercopy.c:250 [inline] __check_object_size+0x5c5/0x780 mm/usercopy.c:215 check_object_size include/linux/ucopysize.h:22 [inline] check_copy_size include/linux/ucopysize.h:59 [inline] copy_to_user include/linux/uaccess.h:219 [inline] listxattr+0xb0/0x170 fs/xattr.c:926 filename_listxattr fs/xattr.c:958 [inline] path_listxattrat+0x137/0x320 fs/xattr.c:988 __do_sys_listxattr fs/xattr.c:1001 [inline] __se_sys_listxattr fs/xattr.c:998 [inline] __x64_sys_listxattr+0x7f/0xd0 fs/xattr.c:998 ...
[CAUSE] Commit 936b8834366e ("ocfs2: Refactor xattr list and remove ocfs2_xattr_handler().") replaced the old per-handler list accounting with ocfs2_xattr_list_entry(), but it kept using size == 0 to detect probe mode.
That assumption stops being true once ocfs2_listxattr() finishes the inline-xattr pass. If the inline names fill the caller buffer exactly, the block-xattr pass runs with a non-NULL buffer and a remaining size of zero. ocfs2_xattr_list_entry() then skips the bounds check, keeps counting block names, and returns a positive size larger than the supplied buffer.
[FIX] Detect probe mode by testing whether the destination buffer pointer is NULL instead of whether the remaining size is zero.
That restores the pre-refactor behavior and matches the OCFS2 getxattr helpers. Once the remaining buffer reaches zero while more names are left, the block-xattr pass now returns -ERANGE instead of reporting a size larger than the allocated list buffer.
AnalysisAI
Memory-safety failure in the Linux kernel OCFS2 filesystem's listxattr() path allows a local low-privileged user to crash the kernel (and potentially leak adjacent kernel heap memory) when an OCFS2 inode carries both inline and block-based extended attributes. Introduced by refactor commit 936b8834366e, the bug causes copy_to_user() to be invoked with a length larger than the allocated list buffer, tripping the hardened usercopy check (kernel BUG at mm/usercopy.c:102). …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires local access with low privileges (CVSS PR:L) and a target system actively using the OCFS2 filesystem; the attacker must be able to influence an OCFS2 inode that holds BOTH inline extended attributes AND block-based extended attributes, with the inline xattr names sized to fill the caller's listxattr() buffer exactly so the subsequent block-xattr pass runs with a non-NULL buffer and zero remaining bytes. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | Signals are internally consistent and point to a moderate, locally-scoped issue rather than an urgent internet-facing threat. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A logged-in local user (or a low-privileged process/container with access to an OCFS2 mount) crafts an inode whose inline extended-attribute names exactly fill a chosen listxattr() buffer while additional block-based xattrs remain, then calls listxattr() with that buffer size. The kernel computes a length larger than the buffer and calls copy_to_user() oversized, triggering a hardened-usercopy BUG and kernel panic (denial of service), or on unhardened kernels copying adjacent kernel heap memory back to the attacker. … |
| Remediation | Vendor-released patch: update to a fixed stable kernel - 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33, or 7.0.10 (or later) on the corresponding branch, or pull your distribution's patched kernel that backports the listxattr probe-mode fix (detecting probe mode by a NULL destination buffer instead of zero remaining size); the fix commits are at git.kernel.org/stable (e.g. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Identify systems running OCFS2 and determine which kernel versions are vulnerable (prior to commit fix 936b8834366e). …
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Same weakness CWE-787 – Out-of-bounds Write
View allSame technique Buffer Overflow
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External POC / Exploit Code
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