{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-90260", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.796Z", "datePublished": "2026-09-17T16:07:58.102Z", "dateUpdated": "2026-10-21T12:50:42.251Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-21T12:50:42.251Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: zoned: don't clobber the extent buffer when zeroing it out\n\nOn a zoned filesystem a freed-but-still-dirty tree block is written out\nas zeros (EXTENT_BUFFER_ZONED_ZEROOUT) only to keep the zone write\npointer advancing. btree_csum_one_bio() implemented this by memzeroing\nthe extent buffer's own folios before submission.\n\nThat destroys the in-memory buffer while it may still be referenced. In\nparticular btrfs_free_tree_block() can run on it afterwards and reads\nthe header to add a delayed reference; once the header has been zeroed\nit frees bytenr 0 and corrupts the extent tree (the\nbtrfs_header_bytenr(buf) != 0 ASSERT in btrfs_free_tree_block(), or an\n\"unable to find ref\" abort). It is flaky and reproduces under fsstress,\ne.g. generic/461 and generic/013.\n\nWrite the zeros to disk from the shared zero page instead and leave the\nextent buffer content untouched, so any later reference - including the\ndelayed reference from btrfs_free_tree_block() - still sees a valid\nheader. end_bbio_meta_write() now clears writeback on the buffer's own\nfolios, as the bio no longer carries them." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H", "baseScore": 7.1, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The trigger is local VFS syscalls on a mounted zoned btrfs: unlink → btrfs_unlink() → btrfs_del_items() → btrfs_clear_buffer_dirty() sets EXTENT_BUFFER_ZONED_ZEROOUT, then fsync → btrfs_sync_file() → btree_writepages() → write_one_eb() → btree_csum_one_bio(). No network protocol carries the data that causes the clobber.\nAC:L - The attacker drives both sides: unlink/write churn that sets ZONED_ZEROOUT in btrfs_clear_buffer_dirty() while leaving DIRTY set, and fsync or btrfs_btree_balance_dirty() running btree_writepages(). lock_extent_buffer_for_io() drops the tree lock before the memzero, and btrfs_del_leaf() unlocks before btrfs_free_tree_block() reads the header.\nPR:L - btrfs_unlink() and btrfs_sync_file() have no capability check; an unprivileged user with write access on the already-mounted zoned volume can COW-free tree blocks and kick metadata writeback (fsync or the btrfs_btree_balance_dirty() at the end of btrfs_unlink()).\nUI:N - The attacker performs the unlink/write/fsync sequence themselves on files they can write; this is a runtime COW/writeback race on a legitimate zoned btrfs (reproduced by fsstress generic/461 and generic/013), not a crafted image a victim must mount.\nS:U - The clobbered extent-buffer folios and the bad delayed refs stay inside this mount's btrfs metadata in the host kernel; there is no KVM/Xen guest-to-host, IOMMU, or sandbox boundary crossing.\nC:N - btree_csum_one_bio() calls memzero_extent_buffer(eb, 0, eb->len), which memset_extent_buffer() restricts to that buffer's own folios via check_eb_range(); the overwrite is zeros, not an out-of-bounds read or kernel-pointer leak.\nI:H - After the header is zeroed, btrfs_free_tree_block() queues a BTRFS_DROP_DELAYED_REF with owning_root=btrfs_header_owner(buf)==0 and level=btrfs_header_level(buf)==0, so __btrfs_free_extent() applies a mismatched backref to the shared extent tree and corrupts metadata for every file on the volume.\nA:H - The mismatched delayed ref hits abort_and_dump() → btrfs_abort_transaction(-EUCLEAN) → __btrfs_handle_fs_error() → btrfs_set_sb_rdonly(), forcing the whole filesystem read-only; with CONFIG_BTRFS_ASSERT, ASSERT(btrfs_header_bytenr(buf) != 0) in btrfs_free_tree_block() panics." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/btrfs/disk-io.c", "fs/btrfs/extent_io.c" ], "versions": [ { "version": "aa6313e6ff2bfbf736a2739047bba355d8241584", "lessThan": "efa5084d08030aa557fdefa3e4a73b2501b7d207", "status": "affected", "versionType": "git" }, { "version": "aa6313e6ff2bfbf736a2739047bba355d8241584", "lessThan": "92484ad014f2e2b0e0e7bbc1610951e978cf557c", "status": "affected", "versionType": "git" }, { "version": "aa6313e6ff2bfbf736a2739047bba355d8241584", "lessThan": "98e3747587f9f87f010d8d7e55786216249a94af", "status": "affected", "versionType": "git" }, { "version": "aa6313e6ff2bfbf736a2739047bba355d8241584", "lessThan": "db4b9eefc8ee0bcaeee4d5e6a7313905f6a2fe7c", "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/disk-io.c", "fs/btrfs/extent_io.c" ], "versions": [ { "version": "6.8", "status": "affected" }, { "version": "0", "lessThan": "6.8", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.114", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.52", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.6", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "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": "6.8", "versionEndExcluding": "6.12.114" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.8", "versionEndExcluding": "6.18.52" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.8", "versionEndExcluding": "7.2.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.8", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/efa5084d08030aa557fdefa3e4a73b2501b7d207" }, { "url": "https://git.kernel.org/stable/c/92484ad014f2e2b0e0e7bbc1610951e978cf557c" }, { "url": "https://git.kernel.org/stable/c/98e3747587f9f87f010d8d7e55786216249a94af" }, { "url": "https://git.kernel.org/stable/c/db4b9eefc8ee0bcaeee4d5e6a7313905f6a2fe7c" } ], "title": "btrfs: zoned: don't clobber the extent buffer when zeroing it out", "x_generator": { "engine": "bippy-1.2.0" } } } }