CVE-2020-36791

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2020-36791", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-02-26T17:07:27.435Z", "datePublished": "2025-05-07T13:17:33.882Z", "dateUpdated": "2026-08-05T08:44:33.087Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T08:44:33.087Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: keep alloc_hash updated after hash allocation\n\nIn commit 599be01ee567 (\"net_sched: fix an OOB access in cls_tcindex\")\nI moved cp->hash calculation before the first\ntcindex_alloc_perfect_hash(), but cp->alloc_hash is left untouched.\nThis difference could lead to another out of bound access.\n\ncp->alloc_hash should always be the size allocated, we should\nupdate it after this tcindex_alloc_perfect_hash()."}], "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 - The bug is triggered through the tc filter netlink configuration path (RTM_NEWTFILTER \u2192 tc_new_tfilter \u2192 tcindex_change \u2192 tcindex_set_parms), not by processing network packets. Exploitation requires local netlink/syscall access to configure cls_tcindex.\nAC:L - An attacker fully controls both the old and new hash sizes and the filter handle via netlink attributes, so shrinking a perfect hash while using a handle past the newly allocated size reliably produces the OOB access with no race or external conditions.\nPR:L - tc_new_tfilter requires CAP_NET_ADMIN checked with netlink_ns_capable against the network namespace's user_ns, which an unprivileged user can obtain via user namespaces (unshare -Urn) without real root in the init namespace.\nUI:N - The attacker creates and modifies their own tcindex filters in a network namespace they control; no victim action is required.\nS:U - Impact is confined to the host kernel privilege boundary (local memory corruption / privilege escalation) and does not cross VM, IOMMU, or other distinct security authorities.\nC:H - Stale alloc_hash allows OOB reads through tcindex_get/tcindex_lookup (perfect + handle beyond the allocated array), and the heap OOB can be leveraged for arbitrary kernel memory disclosure.\nI:H - tcindex_set_parms does r = cp->perfect + handle then writes result/exts into that slot; with handle past the newly allocated hash this is a controlled heap out-of-bounds write enabling memory corruption and control-flow hijacking.\nA:H - The out-of-bounds access was caught by syzbot as a kernel memory-safety failure and can produce oops/panic or heap corruption leading to a crash even without full exploitation."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/sched/cls_tcindex.c"], "versions": [{"version": "73c29d2f6f8ae731b1e09051b69ed3ba2319482b", "lessThan": "d6cdc5bb19b595486fb2e6661e5138d73a57f454", "status": "affected", "versionType": "git"}, {"version": "b974ac51f5834a729de252fc5c1c9de9efd79b45", "lessThan": "c4453d2833671e3a9f6bd52f0f581056c3736386", "status": "affected", "versionType": "git"}, {"version": "6cb448ee493c8a514c9afa0c346f3f5b3227de85", "lessThan": "9f8b6c44be178c2498a00b270872a6e30e7c8266", "status": "affected", "versionType": "git"}, {"version": "478c4b2ffd44e5186c7e22ae7c38a86a5b9cfde5", "lessThan": "557d015ffb27b672e24e6ad141fd887783871dc2", "status": "affected", "versionType": "git"}, {"version": "dd8142a6fa5270783d415292ec8169f4ea2a5468", "lessThan": "d23faf32e577922b6da20bf3740625c1105381bf", "status": "affected", "versionType": "git"}, {"version": "2c66ff8d08f81bcf8e8cb22e31e39c051b15336a", "lessThan": "bd3ee8fb6371b45c71c9345cc359b94da2ddefa9", "status": "affected", "versionType": "git"}, {"version": "599be01ee567b61f4471ee8078870847d0a11e8e", "lessThan": "0d1c3530e1bd38382edef72591b78e877e0edcd3", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/sched/cls_tcindex.c"], "versions": [{"version": "4.4.214", "lessThan": "4.4.218", "status": "affected", "versionType": "semver"}, {"version": "4.9.214", "lessThan": "4.9.218", "status": "affected", "versionType": "semver"}, {"version": "4.14.171", "lessThan": "4.14.175", "status": "affected", "versionType": "semver"}, {"version": "4.19.103", "lessThan": "4.19.114", "status": "affected", "versionType": "semver"}, {"version": "5.4.19", "lessThan": "5.4.29", "status": "affected", "versionType": "semver"}, {"version": "5.5.3", "lessThan": "5.5.14", "status": "affected", "versionType": "semver"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4.214", "versionEndExcluding": "4.4.218"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.9.214", "versionEndExcluding": "4.9.218"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.14.171", "versionEndExcluding": "4.14.175"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19.103", "versionEndExcluding": "4.19.114"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.4.19", "versionEndExcluding": "5.4.29"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.5.3", "versionEndExcluding": "5.5.14"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/d6cdc5bb19b595486fb2e6661e5138d73a57f454"}, {"url": "https://git.kernel.org/stable/c/c4453d2833671e3a9f6bd52f0f581056c3736386"}, {"url": "https://git.kernel.org/stable/c/9f8b6c44be178c2498a00b270872a6e30e7c8266"}, {"url": "https://git.kernel.org/stable/c/557d015ffb27b672e24e6ad141fd887783871dc2"}, {"url": "https://git.kernel.org/stable/c/d23faf32e577922b6da20bf3740625c1105381bf"}, {"url": "https://git.kernel.org/stable/c/bd3ee8fb6371b45c71c9345cc359b94da2ddefa9"}, {"url": "https://git.kernel.org/stable/c/0d1c3530e1bd38382edef72591b78e877e0edcd3"}, {"url": "https://syzkaller.appspot.com/bug?id=ea260693da894e7b078d18fca2c9c0a19b457534"}, {"url": "https://blog.cdthoughts.ch/2021/03/16/syzbot-bug.html"}], "title": "net_sched: keep alloc_hash updated after hash allocation", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["net/sched/cls_tcindex.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "d6cdc5bb19b595486fb2e6661e5138d73a57f454", "status": "affected", "version": "73c29d2f6f8ae731b1e09051b69ed3ba2319482b", "versionType": "git"}, {"lessThan": "c4453d2833671e3a9f6bd52f0f581056c3736386", "status": "affected", "version": "b974ac51f5834a729de252fc5c1c9de9efd79b45", "versionType": "git"}, {"lessThan": "9f8b6c44be178c2498a00b270872a6e30e7c8266", "status": "affected", "version": "6cb448ee493c8a514c9afa0c346f3f5b3227de85", "versionType": "git"}, {"lessThan": "557d015ffb27b672e24e6ad141fd887783871dc2", "status": "affected", "version": "478c4b2ffd44e5186c7e22ae7c38a86a5b9cfde5", "versionType": "git"}, {"lessThan": "d23faf32e577922b6da20bf3740625c1105381bf", "status": "affected", "version": "dd8142a6fa5270783d415292ec8169f4ea2a5468", "versionType": "git"}, {"lessThan": "bd3ee8fb6371b45c71c9345cc359b94da2ddefa9", "status": "affected", "version": "2c66ff8d08f81bcf8e8cb22e31e39c051b15336a", "versionType": "git"}, {"lessThan": "0d1c3530e1bd38382edef72591b78e877e0edcd3", "status": "affected", "version": "599be01ee567b61f4471ee8078870847d0a11e8e", "versionType": "git"}]}, {"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["net/sched/cls_tcindex.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "4.4.218", "status": "affected", "version": "4.4.214", "versionType": "semver"}, {"lessThan": "4.9.218", "status": "affected", "version": "4.9.214", "versionType": "semver"}, {"lessThan": "4.14.175", "status": "affected", "version": "4.14.171", "versionType": "semver"}, {"lessThan": "4.19.114", "status": "affected", "version": "4.19.103", "versionType": "semver"}, {"lessThan": "5.4.29", "status": "affected", "version": "5.4.19", "versionType": "semver"}, {"lessThan": "5.5.14", "status": "affected", "version": "5.5.3", "versionType": "semver"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "EA46E804-CC77-4E3E-8EFE-1E0D208F2891", "versionEndExcluding": "4.4.218", "versionStartIncluding": "4.4.214", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "532BFC53-5843-4E9A-9AB3-3898853DD42C", "versionEndExcluding": "4.9.218", "versionStartIncluding": "4.9.214", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "26CFC34C-0C30-400B-A805-EBB9AD56155E", "versionEndExcluding": "4.14.175", "versionStartIncluding": "4.14.171", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "05AC3490-6BEC-4FB4-9577-02840D73CE90", "versionEndExcluding": "4.19.114", "versionStartIncluding": "4.19.103", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "9253035D-B349-4044-B4B2-0052B6F8AF01", "versionEndExcluding": "5.4.29", "versionStartIncluding": "5.4.19", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "AF089097-DB58-4F52-AC68-3418ADEE10A2", "versionEndExcluding": "5.5.14", "versionStartIncluding": "5.5.3", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.6:rc1:*:*:*:*:*:*", "matchCriteriaId": "F5DAF39E-0835-49B4-8221-7FCE81692A4B", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.6:rc2:*:*:*:*:*:*", "matchCriteriaId": "73DFCE15-1BB8-4740-B9CD-57F2DF3EA15D", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.6:rc3:*:*:*:*:*:*", "matchCriteriaId": "7D3107F6-EB44-4C65-AA1B-1E96923F6409", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.6:rc4:*:*:*:*:*:*", "matchCriteriaId": "DC0C894E-6323-44E5-89DD-8FB6A5C41CAF", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.6:rc5:*:*:*:*:*:*", "matchCriteriaId": "4C76EAC9-C2E6-4B6F-B002-ADBE74DDD794", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.6:rc6:*:*:*:*:*:*", "matchCriteriaId": "F13B8FBF-E007-4F60-A290-2833B45F8520", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.6:rc7:*:*:*:*:*:*", "matchCriteriaId": "CD0276C4-2C60-4C52-AC89-F96DF991B858", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: keep alloc_hash updated after hash allocation\n\nIn commit 599be01ee567 (\"net_sched: fix an OOB access in cls_tcindex\")\nI moved cp->hash calculation before the first\ntcindex_alloc_perfect_hash(), but cp->alloc_hash is left untouched.\nThis difference could lead to another out of bound access.\n\ncp->alloc_hash should always be the size allocated, we should\nupdate it after this tcindex_alloc_perfect_hash()."}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net_sched: mantener alloc_hash actualizado tras la asignaci\u00f3n de hash. En el commit 599be01ee567 (\"net_sched: corregir un acceso OOB en cls_tcindex\"), se movi\u00f3 el c\u00e1lculo de cp->hash antes del primer tcindex_alloc_perfect_hash(), pero se mantuvo intacto. Esta diferencia podr\u00eda provocar otro acceso fuera de los l\u00edmites. cp->alloc_hash siempre debe tener el tama\u00f1o asignado; debemos actualizarlo despu\u00e9s de este tcindex_alloc_perfect_hash()."}], "id": "CVE-2020-36791", "lastModified": "2026-08-04T10:16:35.580", "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": 7.1, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.2, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2025-05-07T14:15:28.513", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Third Party Advisory"], "url": "https://blog.cdthoughts.ch/2021/03/16/syzbot-bug.html"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/0d1c3530e1bd38382edef72591b78e877e0edcd3"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/557d015ffb27b672e24e6ad141fd887783871dc2"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/9f8b6c44be178c2498a00b270872a6e30e7c8266"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/bd3ee8fb6371b45c71c9345cc359b94da2ddefa9"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/c4453d2833671e3a9f6bd52f0f581056c3736386"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d23faf32e577922b6da20bf3740625c1105381bf"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d6cdc5bb19b595486fb2e6661e5138d73a57f454"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Issue Tracking"], "url": "https://syzkaller.appspot.com/bug?id=ea260693da894e7b078d18fca2c9c0a19b457534"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-125"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: net_sched: keep alloc_hash updated after hash allocation", "id": "2364708", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2364708"}, "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"}, "details": ["In the Linux kernel, the following vulnerability has been resolved:\nnet_sched: keep alloc_hash updated after hash allocation\nIn commit 599be01ee567 (\"net_sched: fix an OOB access in cls_tcindex\")\nI moved cp->hash calculation before the first\ntcindex_alloc_perfect_hash(), but cp->alloc_hash is left untouched.\nThis difference could lead to another out of bound access.\ncp->alloc_hash should always be the size allocated, we should\nupdate it after this tcindex_alloc_perfect_hash()."], "name": "CVE-2020-36791", "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": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "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": "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"}], "public_date": "2025-05-07T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2020-36791\nhttps://nvd.nist.gov/vuln/detail/CVE-2020-36791\nhttps://lore.kernel.org/linux-cve-announce/2025050736-CVE-2020-36791-4c86@gregkh/T"], "threat_severity": "Moderate"}

{"created": "2025-07-12T22:23:44.771128+00:00", "updated": "2025-07-12T22:23:44.771174+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}