{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2021-47243", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-04-10T18:59:19.532Z", "datePublished": "2024-05-21T14:19:42.309Z", "dateUpdated": "2026-08-05T08:46:54.221Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T08:46:54.221Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsch_cake: Fix out of bounds when parsing TCP options and header\n\nThe TCP option parser in cake qdisc (cake_get_tcpopt and\ncake_tcph_may_drop) could read one byte out of bounds. When the length\nis 1, the execution flow gets into the loop, reads one byte of the\nopcode, and if the opcode is neither TCPOPT_EOL nor TCPOPT_NOP, it reads\none more byte, which exceeds the length of 1.\n\nThis fix is inspired by commit 9609dad263f8 (\"ipv4: tcp_input: fix stack\nout of bounds when parsing TCP options.\").\n\nv2 changes:\n\nAdded doff validation in cake_get_tcphdr to avoid parsing garbage as TCP\nheader. Although it wasn't strictly an out-of-bounds access (memory was\nallocated), garbage values could be read where CAKE expected the TCP\nheader if doff was smaller than 5." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H", "baseScore": 7.1, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The vulnerable TCP option parsers run in the CAKE qdisc (net/sched) during enqueue after the qdisc is attached via tc/netlink; qdisc bugs are local, and an attacker reaches them by configuring cake in a netns and sending crafted packets through it.\nAC:L - The attacker fully controls qdisc setup (enabling ack_filter) and the TCP option bytes that trigger the length==1 path, so the one-byte out-of-bounds read is reliably reproducible with no conditions outside attacker control.\nPR:L - Creating/changing the cake qdisc requires CAP_NET_ADMIN, but that capability is obtainable in an unprivileged user namespace via netlink_net_capable(sock_net()->user_ns), so only low privileges are required.\nUI:N - No victim interaction is needed; the attacker configures the qdisc and injects the crafted TCP packets themselves.\nS:U - Impact remains within the same kernel/host security authority; this is not a VM escape, IOMMU bypass, or other cross-boundary breakout.\nC:H - The bug is an out-of-bounds read of adjacent skb/stack memory past the TCP options; per scoring guidance OOB reads are treated as high confidentiality impact when they may expose adjacent kernel memory.\nI:N - The out-of-bounds access is a read only; the byte is used solely as opsize and then rejected by the existing bounds check, with no write primitive or controllable data modification.\nA:H - Reading one byte past valid packet/header data can fault when that address is unmapped or otherwise invalid, causing a kernel oops/panic and full availability loss." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sched/sch_cake.c" ], "versions": [ { "version": "8b7138814f29933898ecd31dfc83e35a30ee69f5", "lessThan": "595897ef118d6fe66690c4fc5b572028c9da95b7", "status": "affected", "versionType": "git" }, { "version": "8b7138814f29933898ecd31dfc83e35a30ee69f5", "lessThan": "4cefa061fc63f4d2dff5ab4083f43857cd7a2335", "status": "affected", "versionType": "git" }, { "version": "8b7138814f29933898ecd31dfc83e35a30ee69f5", "lessThan": "3b491dd593d582ceeb27aa617600712a6bd14246", "status": "affected", "versionType": "git" }, { "version": "8b7138814f29933898ecd31dfc83e35a30ee69f5", "lessThan": "3371392c60e2685af30bd4547badd880f5df2b3f", "status": "affected", "versionType": "git" }, { "version": "8b7138814f29933898ecd31dfc83e35a30ee69f5", "lessThan": "ba91c49dedbde758ba0b72f57ac90b06ddf8e548", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sched/sch_cake.c" ], "versions": [ { "version": "4.19", "status": "affected" }, { "version": "0", "lessThan": "4.19", "status": "unaffected", "versionType": "semver" }, { "version": "4.19.196", "lessThanOrEqual": "4.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.4.128", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.46", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.12.13", "lessThanOrEqual": "5.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.13", "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": "4.19", "versionEndExcluding": "4.19.196" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19", "versionEndExcluding": "5.4.128" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19", "versionEndExcluding": "5.10.46" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19", "versionEndExcluding": "5.12.13" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19", "versionEndExcluding": "5.13" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/595897ef118d6fe66690c4fc5b572028c9da95b7" }, { "url": "https://git.kernel.org/stable/c/4cefa061fc63f4d2dff5ab4083f43857cd7a2335" }, { "url": "https://git.kernel.org/stable/c/3b491dd593d582ceeb27aa617600712a6bd14246" }, { "url": "https://git.kernel.org/stable/c/3371392c60e2685af30bd4547badd880f5df2b3f" }, { "url": "https://git.kernel.org/stable/c/ba91c49dedbde758ba0b72f57ac90b06ddf8e548" } ], "title": "sch_cake: Fix out of bounds when parsing TCP options and header", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-04T05:32:07.942Z" }, "title": "CVE Program Container", "references": [ { "url": "https://git.kernel.org/stable/c/595897ef118d6fe66690c4fc5b572028c9da95b7", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/4cefa061fc63f4d2dff5ab4083f43857cd7a2335", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/3b491dd593d582ceeb27aa617600712a6bd14246", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/3371392c60e2685af30bd4547badd880f5df2b3f", "tags": [ "x_transferred" ] }, { "url": 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