{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2021-47244","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2024-04-10T18:59:19.533Z","datePublished":"2024-05-21T14:19:42.983Z","dateUpdated":"2026-08-05T08:46:55.302Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T08:46:55.302Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: Fix out of bounds when parsing TCP options\n\nThe TCP option parser in mptcp (mptcp_get_options) could read one byte\nout of bounds. When the length is 1, the execution flow gets into the\nloop, reads one byte of the opcode, and if the opcode is neither\nTCPOPT_EOL nor TCPOPT_NOP, it reads one more byte, which exceeds the\nlength of 1.\n\nThis fix is inspired by commit 9609dad263f8 (\"ipv4: tcp_input: fix stack\nout of bounds when parsing TCP options.\")."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H","baseScore":8.2,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - mptcp_get_options() parses TCP options from received skbs on MPTCP sockets, including unauthenticated SYNs in subflow_check_req(), established-path mptcp_incoming_options(), and peer SYN-ACKs in subflow_finish_connect(), so a remote peer triggers it via crafted TCP packets.\nAC:L - The attacker fully controls the TCP option bytes and can reliably leave a 1-byte remainder (e.g., NOP padding or a 3-byte option in a 4-byte options area) with a non-EOL/non-NOP opcode so the missing length<2 check is hit every time.\nPR:N - The vulnerable parser runs on the pre-accept SYN path and on ordinary MPTCP segment receive with no credential or capability check; any network peer that can send TCP segments to an MPTCP socket can reach it.\nUI:N - Against an MPTCP listener or an existing MPTCP connection, exploitation is by sending packets alone and does not require a separate user to open a file, mount something, or otherwise interact.\nS:U - Impact is confined to the host kernel that parses the packet; this is ordinary in-kernel memory-safety exposure, not a VM/IOMMU/sandbox boundary cross.\nC:L - The bug is a single-byte out-of-bounds read past the doff-bounded options (into payload, skb tailroom, or skb_shared_info); per guidance that is a bounded OOB read, so confidentiality is Low rather than High.\nI:N - There is no out-of-bounds write; when length==1 the wrongly read opsize is only compared and then the function returns, so it cannot be turned into a memory write or control-flow hijack primitive.\nA:H - Reading one byte past the validated TCP header length can touch memory outside skb->len and can oops/fault depending on skb layout (and is a hard failure under KASAN), so availability impact is scored High under the overestimate rule."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/mptcp/options.c"],"versions":[{"version":"cec37a6e41aae7bf3df9a3da783380a4d9325fd8","lessThan":"73eeba71dc9932970befa009e68272a3d5ec4a58","status":"affected","versionType":"git"},{"version":"cec37a6e41aae7bf3df9a3da783380a4d9325fd8","lessThan":"76e02b8905d0691e89e104a882f3bba7dd0f6037","status":"affected","versionType":"git"},{"version":"cec37a6e41aae7bf3df9a3da783380a4d9325fd8","lessThan":"07718be265680dcf496347d475ce1a5442f55ad7","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/mptcp/options.c"],"versions":[{"version":"5.6","status":"affected"},{"version":"0","lessThan":"5.6","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":"5.6","versionEndExcluding":"5.10.46"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"5.12.13"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"5.13"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/73eeba71dc9932970befa009e68272a3d5ec4a58"},{"url":"https://git.kernel.org/stable/c/76e02b8905d0691e89e104a882f3bba7dd0f6037"},{"url":"https://git.kernel.org/stable/c/07718be265680dcf496347d475ce1a5442f55ad7"}],"title":"mptcp: Fix out of bounds when parsing TCP options","x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"problemTypes":[{"descriptions":[{"type":"CWE","lang":"en","description":"CWE-noinfo Not enough information"}]}],"metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":6.2,"attackVector":"LOCAL","baseSeverity":"MEDIUM","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","integrityImpact":"NONE","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"HIGH","privilegesRequired":"NONE","confidentialityImpact":"NONE"}},{"other":{"type":"ssvc","content":{"timestamp":"2024-05-31T18:50:36.202074Z","id":"CVE-2021-47244","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2024-11-05T21:23:21.293Z"}},{"providerMetadata":{"orgId":"af854a3a-2127-422b-91ae-364da2661108","shortName":"CVE","dateUpdated":"2024-08-04T05:32:07.998Z"},"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/73eeba71dc9932970befa009e68272a3d5ec4a58","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/76e02b8905d0691e89e104a882f3bba7dd0f6037","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/07718be265680dcf496347d475ce1a5442f55ad7","tags":["x_transferred"]}]}]}}