{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-93798", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-18T17:59:28.789Z", "datePublished": "2026-09-24T16:02:31.291Z", "dateUpdated": "2026-10-03T10:57:32.550Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-03T10:57:32.550Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix reloc root cleanup in merge_reloc_roots()\n\nIf the root we got has zero root refs in its root item, we are resetting\nthe root's ->reloc_root without using barriers like we do everywhere else.\nSashiko complained about this while reviewing another patch, and it's\ncorrect (see the Link tag below).\n\nAlso, we should not clear BTRFS_ROOT_DEAD_RELOC_TREE from the root unless\nthe root points to the reloc root we have.\n\nFix this by using clear_reloc_root(), which issues the memory barrier\nafter setting the root's ->reloc_root to NULL and before clearing the bit\nBTRFS_ROOT_DEAD_RELOC_TREE from the root."}], "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 - merge_reloc_roots() is reached from local VFS activity: unlink/write call btrfs_update_block_group() which btrfs_mark_bg_to_reclaim(); btrfs_reclaim_bgs_work() then runs btrfs_relocate_chunk()->btrfs_relocate_block_group()->relocate_block_group()->prepare_to_merge()->merge_reloc_roots(). No network protocol supplies the causing state.\nAC:L - When relocate_block_group() fails (the attacker can force ENOSPC via extra allocations), prepare_to_merge() leaves reloc roots at 0 refs and merge_reloc_roots() NULLs root->reloc_root then clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE) without smp_wmb(). Concurrent writes invoke btrfs_init_reloc_root()/have_reloc_root() on that same root, so the attacker drives both sides.\nPR:L - BTRFS_IOC_BALANCE requires capable(CAP_SYS_ADMIN), but btrfs_buffered_write() and unlink used to mark a block group reclaimable have no capability gate. btrfs_fs_type lacks FS_USERNS_MOUNT, so the volume is admin-mounted, yet any unprivileged uid with write permission on that mount can induce reclaim into merge_reloc_roots().\nUI:N - The attacker induces the 0-ref merge_reloc_roots() cleanup with their own writes and deletions on a btrfs they can already write, then races have_reloc_root() with further writes or btrfs_ioctl_snap_create(); no second user needs to mount an image or run balance.\nS:U - The use-after-free is of the struct btrfs_root stored in fs_root->reloc_root inside the same host kernel that mounted the volume; merge_reloc_roots() does not cross a VM, IOMMU, or sandbox authority.\nC:H - Missing smp_wmb() in merge_reloc_roots() lets have_reloc_root() see BTRFS_ROOT_DEAD_RELOC_TREE already clear while still loading the old root->reloc_root pointer; btrfs_should_ignore_reloc_root() then reads reloc_root->commit_root after the matching btrfs_put_root() dropped that reloc root.\nI:H - The same stale reloc_root is written by btrfs_init_reloc_root() via btrfs_set_root_last_trans() and by commit_fs_roots()->btrfs_update_reloc_root() which mutates reloc_root->root_item, giving a write-after-free of struct btrfs_root.\nA:H - Using the dangling reloc_root after merge_reloc_roots()'s btrfs_put_root() oopses; if clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE) becomes visible while the pointer still refers to the 0-ref tree, btrfs_reloc_pre_snapshot() hits BUG_ON(btrfs_root_refs(&root->root_item)==0)."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/btrfs/relocation.c"], "versions": [{"version": 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"b78fe9563e2d5ae47805f1e5dc722c91fd30e1f8", "status": "affected", "versionType": "git"}, {"version": "ee08663380ffd5a45a1c87580fbc305e8413c235", "status": "affected", "versionType": "git"}, {"version": "33823378ff2b510fd7b566f25bb18438aeb9b23b", "status": "affected", "versionType": "git"}, {"version": "5.4.54", "lessThan": "5.5", "status": "affected", "versionType": "semver"}, {"version": "5.7.11", "lessThan": "5.8", "status": "affected", "versionType": "semver"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/btrfs/relocation.c"], "versions": [{"version": "5.8", "status": "affected"}, {"version": "0", "lessThan": "5.8", "status": "unaffected", "versionType": "semver"}, {"version": "5.10.271", "lessThanOrEqual": "5.10.*", "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": "5.8", "versionEndExcluding": "5.10.271"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.8", "versionEndExcluding": "5.15.222"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", 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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["fs/btrfs/relocation.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "29531470b1bf1e8bd2df4941fe913106edbca615", "status": "affected", "version": "1dae7e0e58b484eaa43d530f211098fdeeb0f404", "versionType": "git"}, {"lessThan": "415f8665a969d3c906e4fd7c90fcbb4b357886f6", "status": "affected", "version": "1dae7e0e58b484eaa43d530f211098fdeeb0f404", "versionType": "git"}, {"lessThan": "ee695a968aa73b1e67ccbf2133dc0e54381d32b2", "status": "affected", "version": "1dae7e0e58b484eaa43d530f211098fdeeb0f404", "versionType": "git"}, {"lessThan": "0bc25f0a2d1b3e0a691431c4d7aef36afcd527c5", "status": "affected", "version": "1dae7e0e58b484eaa43d530f211098fdeeb0f404", "versionType": "git"}, {"lessThan": "ab48583aa9948205ff9a6470e23dbff74c565e24", "status": "affected", "version": "1dae7e0e58b484eaa43d530f211098fdeeb0f404", "versionType": "git"}, {"lessThan": "63d6b1f04cd91c825329712aa526215ffa5d11ca", "status": "affected", "version": "1dae7e0e58b484eaa43d530f211098fdeeb0f404", "versionType": "git"}, {"lessThan": "b78fe9563e2d5ae47805f1e5dc722c91fd30e1f8", "status": "affected", "version": "1dae7e0e58b484eaa43d530f211098fdeeb0f404", "versionType": "git"}, {"status": "affected", "version": "ee08663380ffd5a45a1c87580fbc305e8413c235", "versionType": "git"}, {"status": "affected", "version": "33823378ff2b510fd7b566f25bb18438aeb9b23b", "versionType": "git"}, {"lessThan": "5.5", "status": "affected", "version": "5.4.54", "versionType": "semver"}, {"lessThan": "5.8", "status": "affected", "version": "5.7.11", "versionType": "semver"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["fs/btrfs/relocation.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "5.8"}, {"lessThan": "5.8", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "5.10.*", "status": "unaffected", "version": "5.10.271", "versionType": "semver"}, {"lessThanOrEqual": "5.15.*", "status": "unaffected", "version": "5.15.222", "versionType": "semver"}, {"lessThanOrEqual": "6.1.*", "status": "unaffected", "version": "6.1.189", "versionType": "semver"}, {"lessThanOrEqual": "6.6.*", "status": "unaffected", "version": "6.6.158", "versionType": "semver"}, {"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.111", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.53", "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\nbtrfs: fix reloc root cleanup in merge_reloc_roots()\n\nIf the root we got has zero root refs in its root item, we are resetting\nthe root's ->reloc_root without using barriers like we do everywhere else.\nSashiko complained about this while reviewing another patch, and it's\ncorrect (see the Link tag below).\n\nAlso, we should not clear BTRFS_ROOT_DEAD_RELOC_TREE from the root unless\nthe root points to the reloc root we have.\n\nFix this by using clear_reloc_root(), which issues the memory barrier\nafter setting the root's ->reloc_root to NULL and before clearing the bit\nBTRFS_ROOT_DEAD_RELOC_TREE from the root."}], "id": "CVE-2026-93798", "lastModified": "2026-10-03T11:17:49.337", "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": "2026-09-24T17:17:12.607", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/0bc25f0a2d1b3e0a691431c4d7aef36afcd527c5"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/29531470b1bf1e8bd2df4941fe913106edbca615"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/415f8665a969d3c906e4fd7c90fcbb4b357886f6"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/63d6b1f04cd91c825329712aa526215ffa5d11ca"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/ab48583aa9948205ff9a6470e23dbff74c565e24"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/b78fe9563e2d5ae47805f1e5dc722c91fd30e1f8"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/ee695a968aa73b1e67ccbf2133dc0e54381d32b2"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{"bugzilla": {"description": "kernel: btrfs: fix reloc root cleanup in merge_reloc_roots()", "id": "2540560", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2540560"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-366", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nbtrfs: fix reloc root cleanup in merge_reloc_roots()\nIf the root we got has zero root refs in its root item, we are resetting\nthe root's ->reloc_root without using barriers like we do everywhere else.\nSashiko complained about this while reviewing another patch, and it's\ncorrect (see the Link tag below).\nAlso, we should not clear BTRFS_ROOT_DEAD_RELOC_TREE from the root unless\nthe root points to the reloc root we have.\nFix this by using clear_reloc_root(), which issues the memory barrier\nafter setting the root's ->reloc_root to NULL and before clearing the bit\nBTRFS_ROOT_DEAD_RELOC_TREE from the root.", "A flaw was found in the Linux kernel's Btrfs file system. A local user could exploit this flaw to cause a Denial of Service (DoS) by triggering system instability or a kernel crash. This issue is caused by missing memory barriers and improper state flag management during relocation root cleanup, which can lead to a race condition when resetting root references."], "name": "CVE-2026-93798", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "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"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Not affected", "package_name": "openshift/ose-rhel-coreos-8", "product_name": "Red Hat OpenShift Container Platform 4"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Not affected", "package_name": "openshift/ose-rhel-coreos-9", "product_name": "Red Hat OpenShift Container Platform 4"}], "public_date": "2026-09-24T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-93798\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-93798\nhttps://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-93798.mbox"], "threat_severity": "Low"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,ab48583aa9948205ff9a6470e23dbff74c565e24)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,63d6b1f04cd91c825329712aa526215ffa5d11ca)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,b78fe9563e2d5ae47805f1e5dc722c91fd30e1f8)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,6.12.111)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,6.18.53)"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.12.111,6.13.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.18.53,6.19.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[7.2,*]"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}], "created": "2026-09-24T20:00:11.013532+00:00", "updated": "2026-10-01T20:15:12.381097+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}