{ "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 → tc_new_tfilter → tcindex_change → 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" } } } }