CVE-2021-47646

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the attacker triggers the bug solely through their own I/O and process/cgroup activity.\nS:U - Impact is confined to the local kernel's security authority (memory corruption / privilege escalation on the host); there is no VM escape, IOMMU bypass, or other cross-boundary scope change.\nC:H - The issue is a use-after-free of bfq_queue objects (dangling last_bfqq_created / broken merge state), which per kernel CVSS guidance yields an arbitrary-read primitive via heap reuse of the freed object.\nI:H - The same UAF/memory-corruption condition enables heap spraying and arbitrary-write / control-flow hijacking in kernel context, so integrity impact is High.\nA:H - The bug causes kernel oops/BUG_ON and slab freelist corruption (demonstrated in bugzilla 214503 crashes in bfq_get_queue / bfq_do_early_stable_merge), so availability impact is High."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["block/bfq-iosched.c"], "versions": [{"version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c", "lessThan": "65d8a737452e88f251fe5d925371de6d606df613", "status": "affected", "versionType": "git"}, {"version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c", "lessThan": "abc2129e646af7b43025d90a071f83043f1ae76c", "status": "affected", "versionType": "git"}, {"version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c", "lessThan": "4083925bd6dc89216d156474a8076feec904e607", "status": "affected", "versionType": "git"}, {"version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c", "lessThan": "15729ff8143f8135b03988a100a19e66d7cb7ecd", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["block/bfq-iosched.c"], "versions": [{"version": "5.13", "status": "affected"}, {"version": "0", "lessThan": "5.13", "status": "unaffected", "versionType": "semver"}, {"version": "5.15.33", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.16.19", "lessThanOrEqual": "5.16.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.17.2", "lessThanOrEqual": "5.17.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.18", "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": "5.13", "versionEndExcluding": "5.15.33"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.13", "versionEndExcluding": "5.16.19"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.13", "versionEndExcluding": "5.17.2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.13", "versionEndExcluding": "5.18"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/65d8a737452e88f251fe5d925371de6d606df613"}, {"url": "https://git.kernel.org/stable/c/abc2129e646af7b43025d90a071f83043f1ae76c"}, {"url": "https://git.kernel.org/stable/c/4083925bd6dc89216d156474a8076feec904e607"}, {"url": "https://git.kernel.org/stable/c/15729ff8143f8135b03988a100a19e66d7cb7ecd"}], "title": "Revert \"Revert \"block, bfq: honor already-setup queue merges\"\"", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.8, "attackVector": "LOCAL", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH"}}, {"other": {"type": "ssvc", "content": {"id": "CVE-2021-47646", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2025-02-27T17:59:39.194997Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-416", "description": "CWE-416 Use After Free"}]}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2025-02-27T18:02:30.637Z"}}]}}

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it is not reachable from network packet processing.\nAC:L - An unprivileged attacker can reliably drive the buggy path by spawning processes that issue concurrent I/O and by migrating between blkcgs so queues are created, merged, moved, and freed under attacker control; success does not depend on victim state beyond BFQ being the active scheduler.\nPR:L - Only an unprivileged local account is required to submit I/O on a BFQ-scheduled device; changing the elevator needs privileges, but BFQ (with group I/O scheduling) is a common/default deployment (e.g. Android), so the attacker need not already be root.\nUI:N - Exploitation requires no action by another user; the attacker triggers the bug solely through their own I/O and process/cgroup activity.\nS:U - Impact is confined to the local kernel's security authority (memory corruption / privilege escalation on the host); there is no VM escape, IOMMU bypass, or other cross-boundary scope change.\nC:H - The issue is a use-after-free of bfq_queue objects (dangling last_bfqq_created / broken merge state), which per kernel CVSS guidance yields an arbitrary-read primitive via heap reuse of the freed object.\nI:H - The same UAF/memory-corruption condition enables heap spraying and arbitrary-write / control-flow hijacking in kernel context, so integrity impact is High.\nA:H - The bug causes kernel oops/BUG_ON and slab freelist corruption (demonstrated in bugzilla 214503 crashes in bfq_get_queue / bfq_do_early_stable_merge), so availability impact is High."}]}], "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c", "lessThan": "65d8a737452e88f251fe5d925371de6d606df613", "versionType": "git"}, {"status": "affected", "version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c", "lessThan": "abc2129e646af7b43025d90a071f83043f1ae76c", "versionType": "git"}, {"status": "affected", "version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c", "lessThan": "4083925bd6dc89216d156474a8076feec904e607", "versionType": "git"}, {"status": "affected", "version": "430a67f9d6169a7b3e328bceb2ef9542e4153c7c", "lessThan": "15729ff8143f8135b03988a100a19e66d7cb7ecd", "versionType": "git"}], "programFiles": ["block/bfq-iosched.c"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "5.13"}, {"status": "unaffected", "version": "0", "lessThan": "5.13", "versionType": "semver"}, {"status": "unaffected", "version": "5.15.33", "versionType": "semver", "lessThanOrEqual": "5.15.*"}, {"status": "unaffected", "version": "5.16.19", "versionType": "semver", "lessThanOrEqual": "5.16.*"}, {"status": "unaffected", "version": "5.17.2", "versionType": "semver", "lessThanOrEqual": "5.17.*"}, {"status": "unaffected", "version": "5.18", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["block/bfq-iosched.c"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/65d8a737452e88f251fe5d925371de6d606df613"}, {"url": "https://git.kernel.org/stable/c/abc2129e646af7b43025d90a071f83043f1ae76c"}, {"url": "https://git.kernel.org/stable/c/4083925bd6dc89216d156474a8076feec904e607"}, {"url": "https://git.kernel.org/stable/c/15729ff8143f8135b03988a100a19e66d7cb7ecd"}], "x_generator": {"engine": "bippy-1.2.0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nRevert \"Revert \"block, bfq: honor already-setup queue merges\"\"\n\nA crash [1] happened to be triggered in conjunction with commit\n2d52c58b9c9b (\"block, bfq: honor already-setup queue merges\"). 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The\nlatter was then reverted by commit ebc69e897e17 (\"Revert \"block, bfq:\nhonor already-setup queue merges\"\"). Yet, the reverted commit was not\nthe one introducing the bug. In fact, it actually triggered a UAF\nintroduced by a different commit, and now fixed by commit d29bd41428cf\n(\"block, bfq: reset last_bfqq_created on group change\").\n\nSo, there is no point in keeping commit 2d52c58b9c9b (\"block, bfq:\nhonor already-setup queue merges\") out. This commit restores it.\n\n[1] https://bugzilla.kernel.org/show_bug.cgi?id=214503"}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: Revert \"Revert \"block, bfq: respetar las fusiones de colas ya configuradas\"\" Se produjo un fallo [1] junto con la confirmaci\u00f3n 2d52c58b9c9b (\"block, bfq: respetar las fusiones de colas ya configuradas\"). Esta \u00faltima se revirti\u00f3 mediante la confirmaci\u00f3n ebc69e897e17 (\"Revert \"block, bfq: respetar las fusiones de colas ya configuradas\"\"). Sin embargo, la confirmaci\u00f3n revertida no fue la que introdujo el error. De hecho, activ\u00f3 una UAF introducida por una confirmaci\u00f3n diferente, y ahora corregida por la confirmaci\u00f3n d29bd41428cf (\"block, bfq: restablecer last_bfqq_created al cambiar de grupo\"). Por lo tanto, no tiene sentido mantener la confirmaci\u00f3n 2d52c58b9c9b (\"block, bfq: respetar las fusiones de colas ya configuradas\"). Esta confirmaci\u00f3n la restaura. [1] https://bugzilla.kernel.org/show_bug.cgi?id=214503"}], "id": "CVE-2021-47646", "lastModified": "2026-08-11T03:17:33.693", "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"}, {"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": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2021-47646", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2025-02-27T17:59:39.194997Z", "version": "2.0.3"}}]}, "published": "2025-02-26T06:37:06.390", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/15729ff8143f8135b03988a100a19e66d7cb7ecd"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/4083925bd6dc89216d156474a8076feec904e607"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/65d8a737452e88f251fe5d925371de6d606df613"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/abc2129e646af7b43025d90a071f83043f1ae76c"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"affected_release": [{"advisory": "RHSA-2022:8267", "cpe": "cpe:/a:redhat:enterprise_linux:9", "package": "kernel-0:5.14.0-162.6.1.el9_1", "product_name": "Red Hat Enterprise Linux 9", "release_date": "2022-11-15T00:00:00Z"}, {"advisory": "RHSA-2022:8267", "cpe": "cpe:/o:redhat:enterprise_linux:9", "package": "kernel-0:5.14.0-162.6.1.el9_1", "product_name": "Red Hat Enterprise Linux 9", "release_date": "2022-11-15T00:00:00Z"}], "bugzilla": {"description": "kernel: Revert \"Revert \"block, bfq: honor already-setup queue merges\"\"", "id": "2348285", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2348285"}, "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": "verified"}, "cwe": "CWE-416", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nRevert \"Revert \"block, bfq: honor already-setup queue merges\"\"\nA crash [1] happened to be triggered in conjunction with commit\n2d52c58b9c9b (\"block, bfq: honor already-setup queue merges\"). The\nlatter was then reverted by commit ebc69e897e17 (\"Revert \"block, bfq:\nhonor already-setup queue merges\"\"). Yet, the reverted commit was not\nthe one introducing the bug. In fact, it actually triggered a UAF\nintroduced by a different commit, and now fixed by commit d29bd41428cf\n(\"block, bfq: reset last_bfqq_created on group change\").\nSo, there is no point in keeping commit 2d52c58b9c9b (\"block, bfq:\nhonor already-setup queue merges\") out. This commit restores it.\n[1] https://bugzilla.kernel.org/show_bug.cgi?id=214503"], "name": "CVE-2021-47646", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not 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": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Out of support scope", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-02-26T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-47646\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-47646\nhttps://lore.kernel.org/linux-cve-announce/2025022648-CVE-2021-47646-d726@gregkh/T"], "threat_severity": "Moderate"}

{}