{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-80537", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-26T14:34:25.765Z", "datePublished": "2026-08-26T14:37:12.180Z", "dateUpdated": "2026-08-27T05:01:27.352Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-27T05:01:27.352Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfs: fix off-by-one in rtrefcount btree root level validation\n\nxfs_rtrefcountbt_compute_maxlevels() sets\n\n\tmp->m_rtrefc_maxlevels = min(d_maxlevels, r_maxlevels) + 1;\n\nwhere the trailing \"+ 1\" already accounts for the inode-root level, so the\ndeepest valid on-disk root level is m_rtrefc_maxlevels - 1 and a cursor must\nsatisfy bc_nlevels <= bc_maxlevels (= m_rtrefc_maxlevels).\n\nThe two on-disk validation paths, xfs_rtrefcountbt_verify() and\nxfs_iformat_rtrefcount(), check the root level with \">\" instead of \">=\", so a\ncrafted rtreflink (metadir + realtime + reflink) image whose\n/rtgroups/N.refcount inode has bb_level == m_rtrefc_maxlevels is accepted on\nmount. xfs_rtrefcountbt_init_cursor() then sets bc_nlevels = bb_level + 1,\nexceeding bc_maxlevels by one. Since the xfs_rtrefcountbt_cur slab object is\nsized for exactly bc_maxlevels entries, the first btree op on such a cursor\nindexes bc_levels[m_rtrefc_maxlevels] past the end of the object. This is\nreached by the first rtrefcount cursor built after mount, via log/CoW\nrecovery (xfs_reflink_recover_cow() during xfs_mountfs()) or an\nFS_IOC_GETFSMAP over the realtime device.\n\nReject a root level equal to m_rtrefc_maxlevels, matching the \">=\" form\nalready used by the sibling data-device refcount/rmap verifiers and the\nin-memory rtrmap verifier.\n\n BUG: KASAN: slab-out-of-bounds in xfs_btree_lookup (fs/xfs/libxfs/xfs_btree.c:2101)\n Write of size 2 at addr ffff888018391658 by task exploit/144\n xfs_btree_lookup (fs/xfs/libxfs/xfs_btree.c:2101)\n xfs_btree_query_range (fs/xfs/libxfs/xfs_btree.c:5308)\n xfs_refcount_recover_cow_leftovers (fs/xfs/libxfs/xfs_refcount.c:2113)\n xfs_reflink_recover_cow (fs/xfs/xfs_reflink.c:1085)\n xlog_recover_finish (fs/xfs/xfs_log_recover.c:3551)\n xfs_mountfs (fs/xfs/xfs_mount.c:1158)\n xfs_fs_fill_super (fs/xfs/xfs_super.c:1940)\n get_tree_bdev_flags (fs/super.c:1634)\n vfs_get_tree (fs/super.c:1694)\n path_mount (fs/namespace.c:4161)\n __x64_sys_mount (fs/namespace.c:4367)\n entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)\n The buggy address belongs to the cache xfs_rtrefcountbt_cur of size 216\n The buggy address is located 8 bytes to the right of\n allocated 216-byte region [ffff888018391578, ffff888018391650)\n Kernel panic - not syncing: Fatal exception"}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:L - The bug is reached only through local kernel entry points\u2014mount(2) during xfs_reflink_recover_cow() in xfs_mountfs(), or FS_IOC_GETFSMAP on an already-mounted XFS volume\u2014not via any network-facing protocol handler (NFS/ksmbd/SMB/TCP).\nAC:L - An attacker fully controls the crafted rtreflink image and can set /rtgroups/N.refcount bb_level == m_rtrefc_maxlevels so mount or the first rtrefcount cursor reliably drives xfs_btree_lookup() to write past bc_levels[]; no victim-dependent race or layout luck is required.\nPR:L - Triggering mount of a loop-backed crafted image needs only CAP_SYS_ADMIN inside a user namespace (unshare -Urn), which unprivileged users can obtain on typical systems; FS_IOC_GETFSMAP is additionally reachable with only a readable open file on the mounted filesystem.\nUI:N - In the highest-impact scenario an unprivileged attacker mounts their own malicious XFS image in a user namespace and immediately hits CoW recovery during xfs_mountfs(), with no separate victim action beyond routine local code execution.\nS:U - Exploitation corrupts kernel heap metadata and can panic or compromise the host kernel, but does not cross a CVSS scope boundary such as a VM/hypervisor guest-to-host escape or IOMMU/DMA sandbox breakout.\nC:H - KASAN reports a slab out-of-bounds write in xfs_btree_lookup() past the xfs_rtrefcountbt_cur allocation; such heap corruption can disclose or influence adjacent slab objects and is treated as arbitrary memory-read potential under kernel CVSS guidance.\nI:H - The vulnerability is an out-of-bounds write (2 bytes into bc_levels[m_rtrefc_maxlevels]) on a kmalloc slab cursor object, enabling adjacent-object corruption and further heap shaping toward arbitrary kernel write or code execution.\nA:H - The reported reproducer causes KASAN slab-out-of-bounds followed by kernel panic during mount recovery; any host mounting or querying the malicious rtrefcount metadata can crash or deny service to the entire system."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/xfs/libxfs/xfs_rtrefcount_btree.c"], "versions": [{"version": "9abe03a0e4f978615a2b1b484b8d09ca84c16ea0", "lessThan": "8a0ecae2ecda9f9a83a496ed05c42c4b1f5c3f2d", "status": "affected", "versionType": "git"}, {"version": "9abe03a0e4f978615a2b1b484b8d09ca84c16ea0", "lessThan": "ccebfc309441e0b37b2e6ece90f18810a489d326", "status": "affected", "versionType": "git"}, {"version": "9abe03a0e4f978615a2b1b484b8d09ca84c16ea0", "lessThan": "cc3144da377de5fb422d44a2311f978623f7c900", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/xfs/libxfs/xfs_rtrefcount_btree.c"], "versions": [{"version": "6.14", "status": "affected"}, {"version": "0", "lessThan": "6.14", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.46", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.1.10", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14", "versionEndExcluding": "6.18.46"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14", "versionEndExcluding": "7.1.10"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14", "versionEndExcluding": "7.2"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/8a0ecae2ecda9f9a83a496ed05c42c4b1f5c3f2d"}, {"url": "https://git.kernel.org/stable/c/ccebfc309441e0b37b2e6ece90f18810a489d326"}, {"url": "https://git.kernel.org/stable/c/cc3144da377de5fb422d44a2311f978623f7c900"}], "title": "xfs: fix off-by-one in rtrefcount btree root level validation", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["fs/xfs/libxfs/xfs_rtrefcount_btree.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "8a0ecae2ecda9f9a83a496ed05c42c4b1f5c3f2d", "status": "affected", "version": "9abe03a0e4f978615a2b1b484b8d09ca84c16ea0", "versionType": "git"}, {"lessThan": "ccebfc309441e0b37b2e6ece90f18810a489d326", "status": "affected", "version": "9abe03a0e4f978615a2b1b484b8d09ca84c16ea0", "versionType": "git"}, {"lessThan": "cc3144da377de5fb422d44a2311f978623f7c900", "status": "affected", "version": "9abe03a0e4f978615a2b1b484b8d09ca84c16ea0", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["fs/xfs/libxfs/xfs_rtrefcount_btree.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "6.14"}, {"lessThan": "6.14", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.46", "versionType": "semver"}, {"lessThanOrEqual": "7.1.*", "status": "unaffected", "version": "7.1.10", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.2", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfs: fix off-by-one in rtrefcount btree root level validation\n\nxfs_rtrefcountbt_compute_maxlevels() sets\n\n\tmp->m_rtrefc_maxlevels = min(d_maxlevels, r_maxlevels) + 1;\n\nwhere the trailing \"+ 1\" already accounts for the inode-root level, so the\ndeepest valid on-disk root level is m_rtrefc_maxlevels - 1 and a cursor must\nsatisfy bc_nlevels <= bc_maxlevels (= m_rtrefc_maxlevels).\n\nThe two on-disk validation paths, xfs_rtrefcountbt_verify() and\nxfs_iformat_rtrefcount(), check the root level with \">\" instead of \">=\", so a\ncrafted rtreflink (metadir + realtime + reflink) image whose\n/rtgroups/N.refcount inode has bb_level == m_rtrefc_maxlevels is accepted on\nmount. xfs_rtrefcountbt_init_cursor() then sets bc_nlevels = bb_level + 1,\nexceeding bc_maxlevels by one. Since the xfs_rtrefcountbt_cur slab object is\nsized for exactly bc_maxlevels entries, the first btree op on such a cursor\nindexes bc_levels[m_rtrefc_maxlevels] past the end of the object. This is\nreached by the first rtrefcount cursor built after mount, via log/CoW\nrecovery (xfs_reflink_recover_cow() during xfs_mountfs()) or an\nFS_IOC_GETFSMAP over the realtime device.\n\nReject a root level equal to m_rtrefc_maxlevels, matching the \">=\" form\nalready used by the sibling data-device refcount/rmap verifiers and the\nin-memory rtrmap verifier.\n\n BUG: KASAN: slab-out-of-bounds in xfs_btree_lookup (fs/xfs/libxfs/xfs_btree.c:2101)\n Write of size 2 at addr ffff888018391658 by task exploit/144\n xfs_btree_lookup (fs/xfs/libxfs/xfs_btree.c:2101)\n xfs_btree_query_range (fs/xfs/libxfs/xfs_btree.c:5308)\n xfs_refcount_recover_cow_leftovers (fs/xfs/libxfs/xfs_refcount.c:2113)\n xfs_reflink_recover_cow (fs/xfs/xfs_reflink.c:1085)\n xlog_recover_finish (fs/xfs/xfs_log_recover.c:3551)\n xfs_mountfs (fs/xfs/xfs_mount.c:1158)\n xfs_fs_fill_super (fs/xfs/xfs_super.c:1940)\n get_tree_bdev_flags (fs/super.c:1634)\n vfs_get_tree (fs/super.c:1694)\n path_mount (fs/namespace.c:4161)\n __x64_sys_mount (fs/namespace.c:4367)\n entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)\n The buggy address belongs to the cache xfs_rtrefcountbt_cur of size 216\n The buggy address is located 8 bytes to the right of\n allocated 216-byte region [ffff888018391578, ffff888018391650)\n Kernel panic - not syncing: Fatal exception"}], "id": "CVE-2026-80537", "lastModified": "2026-08-27T06:17:34.210", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}]}, "published": "2026-08-26T15:17:07.890", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/8a0ecae2ecda9f9a83a496ed05c42c4b1f5c3f2d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/cc3144da377de5fb422d44a2311f978623f7c900"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/ccebfc309441e0b37b2e6ece90f18810a489d326"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{"bugzilla": {"description": "kernel: xfs: fix off-by-one in rtrefcount btree root level validation", "id": "2524432", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2524432"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-787", "details": ["A flaw was found in the Linux kernel's XFS filesystem. An off-by-one error in the rtrefcount btree root level validation allows a local attacker to craft a malicious XFS image. When this image is mounted, it can lead to a slab-out-of-bounds write, causing a kernel panic and a denial of service (DoS) on the system."], "name": "CVE-2026-80537", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-08-26T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-80537\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-80537\nhttps://lore.kernel.org/linux-cve-announce/2026082605-CVE-2026-80537-c51a@gregkh/T"], "threat_severity": "Moderate"}