{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-93813", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-18T17:59:28.790Z", "datePublished": "2026-09-24T16:02:49.907Z", "dateUpdated": "2026-10-03T10:57:45.809Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-03T10:57:45.809Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: tree-checker: validate INODE_REF's namelen\n\n[BUG]\nA crafted btrfs image can trigger the following crash:\n\n BUG: unable to handle page fault for address: ffffd1dc42884000\n #PF: supervisor write access in kernel mode\n #PF: error_code(0x0002) - not-present page\n CPU: 9 UID: 0 PID: 1034 Comm: poc Not tainted 7.1.0-rc4-custom+ #383 PREEMPT(full) 46af0a92938a63be7132e0dfd71e62327c51d5c2\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022\n RIP: 0010:memcpy+0xc/0x10\n Call Trace:\n \n read_extent_buffer+0xe4/0x100 [btrfs 3cf0785dd58fec8c5ff84633b772f17ce1f92a8f]\n btrfs_get_name+0x15e/0x1e0 [btrfs 3cf0785dd58fec8c5ff84633b772f17ce1f92a8f]\n reconnect_path+0x165/0x390\n exportfs_decode_fh_raw+0x337/0x400\n ? drop_caches_sysctl_handler+0xb0/0xb0\n \n ---[ end trace 0000000000000000 ]---\n RIP: 0010:memcpy+0xc/0x10\n Kernel panic - not syncing: Fatal exception\n\n[CAUSE]\nTThe crafted image has the following corrupted INODE_REF item:\n\n item 9 key (258 INODE_REF 257) itemoff 11544 itemsize 4106\n \tindex 2 namelen 4096 name: d\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\\000\n\nThe itemsize matches the namelen, but the namelen is 4096, way larger\nthan normal name length limit (BTRFS_NAME_LEN, 255).\n\nMeanwhile the memory of the @name is only 255 byte sized, this will cause\nout-of-boundary access, and cause the above crash.\n\n[FIX]\nAdd extra namelen verification for INODE_REF, just like what we have\ndone in ROOT_REF checks.\n\nNow the crafted image can be rejected gracefully:\n\n BTRFS critical (device dm-2): corrupt leaf: root=5 block=30572544 slot=14 ino=259, invalid inode ref name length, has 4096 expect [1, 255]\n BTRFS error (device dm-2): read time tree block corruption detected on logical 30572544 mirror 2\n\n[ Rebase, add a Link: tag, add an simple cause analyze ]" } ], "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 - check_inode_ref() failed to cap INODE_REF name_len, so a crafted leaf with name_len 4096 is accepted. Those bytes come from the mounted image, not a protocol field. The overflow is open_by_handle_at() → do_handle_to_path() → exportfs_decode_fh_raw() → reconnect_path() → btrfs_get_name(); btrfs_fid has only objectid/gen, so an NFS handle does not carry the bad namelen.\nAC:L - The attacker writes an INODE_REF whose name_len exceeds BTRFS_NAME_LEN (255) but fits the item (PoC: 4096/4106), which the old check_inode_ref() allowed. Mounting that image and calling open_by_handle_at() on a directory filehandle for that inode makes reconnect_path() call btrfs_get_name() every time; no race or uninducible device failure is required.\nPR:L - btrfs_fs_type lacks FS_USERNS_MOUNT, so mount_capable() needs init-ns CAP_SYS_ADMIN, but a local user can mount the image via udisks2/polkit. The trigger is open_by_handle_at(): may_decode_fh() admits ns_capable(current_user_ns(), CAP_DAC_READ_SEARCH) with capable_wrt_mount() and O_DIRECTORY, so userns root on that mount is enough.\nUI:N - The attacker authors the INODE_REF, mounts the image (udisks/loop), and calls open_by_handle_at() so reconnect_path() runs btrfs_get_name() on that inode. That is their own action against data they already control; no second user must open a file or confirm a dialog.\nS:U - btrfs_get_name()'s overflow of exportfs_decode_fh_raw()'s nbuf corrupts the host kernel stack only. It does not cross a KVM/Xen guest-host, IOMMU/DMA, or other security-authority boundary.\nC:H - read_extent_buffer() in btrfs_get_name() memcpy's the attacker-chosen INODE_REF name (PoC namelen 4096) into exportfs_decode_fh_raw()'s nbuf[NAME_MAX+1] (256 bytes). That stack overflow overwrites saved frames and is kernel memory corruption usable for arbitrary disclosure.\nI:H - The same unbounded copy, plus name[name_len]='\\0' at offset 4096, is an attacker-controlled out-of-bounds write into kernel stack in exportfs_decode_fh_raw(). Chosen namelen/name bytes enable return-address overwrite and control-flow hijack, not a bounded metadata tweak.\nA:H - The reporter's PoC faults in memcpy() from read_extent_buffer() called by btrfs_get_name() (supervisor write to an unmapped address) and panics. Any name_len that runs nbuf off the mapped stack oopses the host." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/btrfs/tree-checker.c" ], "versions": [ { "version": "2ede0daf01549cecf4bb0962c46dc47382047523", "lessThan": "60078a3e25c09d9d8fba828b0d81bb33e449a1b2", "status": "affected", "versionType": "git" }, { "version": "2ede0daf01549cecf4bb0962c46dc47382047523", "lessThan": "509d6a4d889e425f305461d8323a7b39ca6c121c", "status": "affected", "versionType": "git" }, { "version": "2ede0daf01549cecf4bb0962c46dc47382047523", "lessThan": "4cb41f07685f88ec724a375883bb0c731db8f6eb", "status": "affected", "versionType": "git" }, { "version": "2ede0daf01549cecf4bb0962c46dc47382047523", "lessThan": "eeddee090b834a7d4b6a8214d2e3739e64c7a338", "status": "affected", "versionType": "git" }, { "version": "2ede0daf01549cecf4bb0962c46dc47382047523", "lessThan": "8f75c19892263bc0555fba922aefe103e841e86d", "status": "affected", "versionType": "git" }, { "version": "2ede0daf01549cecf4bb0962c46dc47382047523", "lessThan": "3dc22abc21f5892406c09202fa2627196cc96967", "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/btrfs/tree-checker.c" ], "versions": [ { "version": "2.6.37", "status": "affected" }, { "version": "0", "lessThan": "2.6.37", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.222", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.189", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.158", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.111", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.53", "lessThanOrEqual": "6.18.*", "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": "2.6.37", "versionEndExcluding": "5.15.222" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.37", "versionEndExcluding": "6.1.189" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.37", "versionEndExcluding": "6.6.158" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.37", "versionEndExcluding": "6.12.111" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.37", "versionEndExcluding": "6.18.53" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.37", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/60078a3e25c09d9d8fba828b0d81bb33e449a1b2" }, { "url": "https://git.kernel.org/stable/c/509d6a4d889e425f305461d8323a7b39ca6c121c" }, { "url": "https://git.kernel.org/stable/c/4cb41f07685f88ec724a375883bb0c731db8f6eb" }, { "url": "https://git.kernel.org/stable/c/eeddee090b834a7d4b6a8214d2e3739e64c7a338" }, { "url": "https://git.kernel.org/stable/c/8f75c19892263bc0555fba922aefe103e841e86d" }, { "url": "https://git.kernel.org/stable/c/3dc22abc21f5892406c09202fa2627196cc96967" } ], "title": "btrfs: tree-checker: validate INODE_REF's namelen", "x_generator": { "engine": "bippy-1.2.0" } } } }