{"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":"https://git.kernel.org/stable/c/ba91c49dedbde758ba0b72f57ac90b06ddf8e548","tags":["x_transferred"]}]},{"metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2021-47243","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical 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