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DEBIAN-CVE-2026-80537
No affected components available
In the Linux kernel, the following vulnerability has been resolved: xfs: fix off-by-one in rtrefcount btree root level validation xfs_rtrefcountbt_compute_maxlevels() sets mp->m_rtrefc_maxlevels = min(d_maxlevels, r_maxlevels) + 1; where the trailing "+ 1" already accounts for the inode-root level, so the deepest valid on-disk root level is m_rtrefc_maxlevels - 1 and a cursor must satisfy bc_nlevels <= bc_maxlevels (= m_rtrefc_maxlevels). The two on-disk validation paths, xfs_rtrefcountbt_verify() and xfs_iformat_rtrefcount(), check the root level with ">" instead of ">=", so a crafted rtreflink (metadir + realtime + reflink) image whose /rtgroups/N.refcount inode has bb_level == m_rtrefc_maxlevels is accepted on mount. xfs_rtrefcountbt_init_cursor() then sets bc_nlevels = bb_level + 1, exceeding bc_maxlevels by one. Since the xfs_rtrefcountbt_cur slab object is sized for exactly bc_maxlevels entries, the first btree op on such a cursor indexes bc_levels[m_rtrefc_maxlevels] past the end of the object. This is reached by the first rtrefcount cursor built after mount, via log/CoW recovery (xfs_reflink_recover_cow() during xfs_mountfs()) or an FS_IOC_GETFSMAP over the realtime device. Reject a root level equal to m_rtrefc_maxlevels, matching the ">=" form already used by the sibling data-device refcount/rmap verifiers and the in-memory rtrmap verifier. BUG: KASAN: slab-out-of-bounds in xfs_btree_lookup (fs/xfs/libxfs/xfs_btree.c:2101) Write of size 2 at addr ffff888018391658 by task exploit/144 xfs_btree_lookup (fs/xfs/libxfs/xfs_btree.c:2101) xfs_btree_query_range (fs/xfs/libxfs/xfs_btree.c:5308) xfs_refcount_recover_cow_leftovers (fs/xfs/libxfs/xfs_refcount.c:2113) xfs_reflink_recover_cow (fs/xfs/xfs_reflink.c:1085) xlog_recover_finish (fs/xfs/xfs_log_recover.c:3551) xfs_mountfs (fs/xfs/xfs_mount.c:1158) xfs_fs_fill_super (fs/xfs/xfs_super.c:1940) get_tree_bdev_flags (fs/super.c:1634) vfs_get_tree (fs/super.c:1694) path_mount (fs/namespace.c:4161) __x64_sys_mount (fs/namespace.c:4367) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) The buggy address belongs to the cache xfs_rtrefcountbt_cur of size 216 The buggy address is located 8 bytes to the right of allocated 216-byte region [ffff888018391578, ffff888018391650) Kernel panic - not syncing: Fatal exception
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The vulnerability requires local access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
- EUVD-2026-66452Upstream
- CVE-2026-80537Upstream
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