{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2026-93800", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-93800", "idYear": 2026, "status": "PUBLISHED", "publishedAt": "2026-09-24T16:02:34.370Z", "updatedAt": "2026-10-03T10:57:34.733Z", "importedAt": "2026-10-24T01:58:41.756Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "btrfs: fix use-after-free on reloc root after error in insert_dirty_subvol()", "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix use-after-free on reloc root after error in insert_dirty_subvol()\n\nIf during relocation we fail in insert_dirty_subvol() because\nbtrfs_update_reloc_root() returned an error, we will leave a root's\nreloc_root field pointing to a reloc root that was freed instead of NULL,\nresulting later in a use-after-free, or double free attempt during\nunmount.\n\nThe sequence of steps is this:\n\n1) During relocation the call to btrfs_update_reloc_root() in\n insert_dirty_subvol() fails, so insert_dirty_subvol() returns the\n error to merge_reloc_root() without adding the root to the list\n rc->dirty_subvol_roots;\n\n2) Then merge_reloc_root() aborts the current transaction because\n insert_dirty_subvol() returned an error;\n\n3) Up the call chain, merge_reloc_roots() gets the error, adds the\n reloc root for root X to the local reloc_roots list and jumps to the\n 'out' label, where it calls free_reloc_roots() to free all the reloc\n roots in the local reloc_roots list. This frees the reloc root for\n root X;\n\n4) We go up the call chain to relocate_block_group() which calls\n clean_dirty_subvols() to go over dirty roots and set their\n ->reloc_root field to NULL, but root X is not in the dirty_subvol_roots\n list, so its ->reloc_root still points to a reloc root;\n\n5) Relocation finishes, with an error and a transaction abort, but the\n ->reloc_root field for root X still points to the reloc root that was\n freed in step 3;\n\n6) When unmounting the fs we end up calling:\n\n btrfs_free_fs_roots()\n btrfs_drop_and_free_fs_root()\n --> calls btrfs_put_root() against root X's ->reloc_root\n which is not NULL and points to the already freed\n reloc root in step 4 above\n\n Resulting in a use-after-free to a double free attempt.\n\nSyzbot reported this with the following dmesg/syslog:\n\n [ 106.004389][ T5339] BTRFS error (device loop0 state A): Transaction aborted (error -5)\n [ 106.014266][ T5339] BTRFS: error (device loop0 state A) in merge_reloc_root:1655: errno=-5 IO failure\n [ 106.021891][ T1061] BTRFS error (device loop0 state A): error while writing out transaction: -5\n [ 106.026964][ T1061] BTRFS warning (device loop0 state A): Skipping commit of aborted transaction.\n [ 106.033807][ T5340] BTRFS error (device loop0 state A): bdev /dev/loop0 errs: wr 3, rd 0, flush 0, corrupt 0, gen 0\n [ 106.039265][ T1061] BTRFS: error (device loop0 state A) in cleanup_transaction:2067: errno=-5 IO failure\n [ 106.044382][ T5339] BTRFS info (device loop0 state EA): forced readonly\n [ 106.074329][ T5339] BTRFS: error (device loop0 state EA) in merge_reloc_roots:1887: errno=-5 IO failure\n [ 106.081004][ T5356] BTRFS info (device loop0 state EA): scrub: started on devid 1\n [ 106.085611][ T5339] BTRFS info (device loop0 state EA): balance: ended with status: -30\n [ 106.089517][ T5356] BTRFS info (device loop0 state EA): scrub: not finished on devid 1 with status: -30\n [ 106.662365][ T5338] BTRFS info (device loop0 state EA): last unmount of filesystem 3a375e4e-b156-4d76-a2ad-16e198ce1409\n [ 106.682946][ T5338] ==================================================================\n [ 106.686574][ T5338] BUG: KASAN: slab-use-after-free in btrfs_put_root+0x2f/0x250\n [ 106.690090][ T5338] Write of size 4 at addr ffff88803f978630 by task syz.0.0/5338\n [ 106.693173][ T5338]\n [ 106.694279][ T5338] CPU: 0 UID: 0 PID: 5338 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full)\n [ 106.694293][ T5338] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\n [ 106.694300][ T5338] Call Trace:\n [ 106.694308][ T5338] \n [ 106.694314][ T5338] dump_stack_lvl+0xe8/0x150\n [ 106.694331][ T5338] print_address_description+0x55/0x1e0\n [ 106.694343][ T5338] ? btrfs_put_root+0x2f/0x250\n [ 106.694358][ T5338] print_report+0x58/0x70\n [ 106.\n---truncated---", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "f32b84d7c977e1906a4781b93b3c93090b6cd675", "status": "affected", "versionType": "git", "lessThan": "5a247097c5f94b51ffc991b444d998ad6e85875f" }, { "version": "592fbcd50c99b8adf999a2a54f9245caff333139", "status": "affected", "versionType": "git", "lessThan": "6372dd394ea907cd85a7a8063db320ec73dfaed0" }, { "version": "592fbcd50c99b8adf999a2a54f9245caff333139", "status": "affected", "versionType": "git", "lessThan": "9f599d120b2b79d2d937c3935b7cdf2697514283" }, { "version": "592fbcd50c99b8adf999a2a54f9245caff333139", "status": "affected", "versionType": "git", "lessThan": "a01837ae174a2a968c245a30e6dd010f50eaf05d" }, { "version": "592fbcd50c99b8adf999a2a54f9245caff333139", "status": "affected", "versionType": "git", "lessThan": "97a540d72ebcb21853d11f2a56782fe377f358e7" }, { "version": "592fbcd50c99b8adf999a2a54f9245caff333139", "status": "affected", "versionType": "git", "lessThan": "fda1b6636ff1846f00643e791099db5564b547d9" }, { "version": "592fbcd50c99b8adf999a2a54f9245caff333139", "status": "affected", "versionType": "git", "lessThan": "83201804efa4a5168be754e1dfc9b2faee760cac" }, { "version": "aa18bc1ff8a51f082d5b3b6d07693797637b4028", "status": "affected", "versionType": "git" }, { "version": "4cb0aea2e250eee35ccfac5f5395cd8f3238a9e5", "status": "affected", "versionType": "git" }, { "version": "5.10.36", "status": "affected", "versionType": "semver", "lessThan": "5.10.271" }, { "version": "5.11.20", "status": "affected", "versionType": "semver", "lessThan": "5.12" }, { "version": "5.12.3", "status": "affected", "versionType": "semver", "lessThan": "5.13" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "5.13", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "5.13" }, { "version": "5.10.271", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.10.*" }, { "version": "5.15.222", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.15.*" }, { "version": "6.1.189", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.1.*" }, { "version": "6.6.158", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.111", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.18.53", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.18.*" }, { "version": "7.2", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }