{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-63828", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.014Z", "datePublished": "2026-07-19T12:02:22.644Z", "dateUpdated": "2026-08-17T04:51:36.839Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T04:51:36.839Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\napparmor: mediate the implicit connect of TCP fast open sendmsg\n\nsendmsg()/sendto() with MSG_FASTOPEN is a combination of connect(2) and\nwrite(2): it opens the connection in the SYN. apparmor_socket_sendmsg()\nonly checks AA_MAY_SEND, so a profile that grants send but denies connect\nlets a confined task open an outbound TCP/MPTCP connection that connect(2)\nwould have refused, bypassing connect mediation.\n\nMediate the implicit connect when MSG_FASTOPEN is set and a destination\nis supplied. Add it to apparmor_socket_sendmsg() (not the shared\naa_sock_msg_perm() helper, which recvmsg also uses) and call aa_sk_perm()\ndirectly, mirroring the selinux and tomoyo fixes. sk_is_tcp() does not\ncover MPTCP fast open, so the SOCK_STREAM/IPPROTO_MPTCP arm is explicit." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N", "baseScore": 8.4, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Exploitation requires a confined local process to invoke sendmsg(2)/sendto(2) with MSG_FASTOPEN; the vulnerable AppArmor LSM hook runs on the syscall path before TCP fast-open performs its implicit connect.\nAC:L - Any confined task that already has send permission can reliably trigger the bypass with a single sendmsg/sendto call using MSG_FASTOPEN and a destination address, with no race or special victim state required beyond TCP Fast Open client support.\nPR:L - The attacker must be an unprivileged process confined by an AppArmor profile that grants network send but denies connect (e.g., hardened Snap/sandboxed service profiles on Ubuntu); no real root or capabilities beyond normal confined-user execution are needed.\nUI:N - No victim interaction is required; the confined attacker process directly issues the bypassing syscall without needing another user or administrator to perform any action.\nS:C - Successful exploitation crosses the AppArmor confinement boundary, allowing a sandboxed task to establish outbound TCP/MPTCP connections that connect(2) mediation would have blocked, escaping the intended network policy scope.\nC:H - Bypassing connect mediation lets a confined process open TCP/MPTCP sessions to destinations policy forbids and read arbitrary response data from those services (internal APIs, metadata endpoints, C2 servers), constituting unauthorized information disclosure.\nI:H - The bypass enables unauthorized outbound connection establishment and transmission of arbitrary application data (including SYN-cookie data) to hosts explicitly denied by the AppArmor connect rule, violating integrity of the confinement policy.\nA:N - This is a pure LSM policy-bypass flaw with no kernel memory corruption, panic, oops, hang, or resource exhaustion; exploitation does not impact system availability." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "security/apparmor/lsm.c" ], "versions": [ { "version": "cf60af03ca4e71134206809ea892e49b92a88896", "lessThan": "a16714e7cf2baa98ba2efddd5d6cbac641f4e76b", "status": "affected", "versionType": "git" }, { "version": "cf60af03ca4e71134206809ea892e49b92a88896", "lessThan": "20383429b56974507c465d016e5238b189f7a246", "status": "affected", "versionType": "git" }, { "version": "cf60af03ca4e71134206809ea892e49b92a88896", "lessThan": "7f57428ce00891d26b0f087ef754a4d820ec83aa", "status": "affected", "versionType": "git" }, { "version": "cf60af03ca4e71134206809ea892e49b92a88896", "lessThan": "faea60deaa05c76f0772650f42eafde12bd39d93", "status": "affected", "versionType": "git" }, { "version": "cf60af03ca4e71134206809ea892e49b92a88896", "lessThan": "07b71c342382b854ab8030b244aeab6a7228ad7d", "status": "affected", "versionType": "git" }, { "version": "cf60af03ca4e71134206809ea892e49b92a88896", "lessThan": "4a69b83045d3195d5b9a9b053ad840ddb2998b4e", "status": "affected", "versionType": "git" }, { "version": "cf60af03ca4e71134206809ea892e49b92a88896", "lessThan": "45ebb934ea50b436ce49b2f159f090dab0d7fa28", "status": "affected", "versionType": "git" }, { "version": "cf60af03ca4e71134206809ea892e49b92a88896", "lessThan": "4d587cd8a72155089a627130bbd4716ec0856e21", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "security/apparmor/lsm.c" ], "versions": [ { "version": "3.6", "status": "affected" }, { "version": "0", "lessThan": "3.6", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.261", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.212", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.177", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.144", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.95", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.38", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.3", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "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": "3.6", "versionEndExcluding": "5.10.261" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "5.15.212" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "6.1.177" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "6.6.144" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "6.12.95" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "6.18.38" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "7.1.3" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.6", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/a16714e7cf2baa98ba2efddd5d6cbac641f4e76b" }, { "url": "https://git.kernel.org/stable/c/20383429b56974507c465d016e5238b189f7a246" }, { "url": "https://git.kernel.org/stable/c/7f57428ce00891d26b0f087ef754a4d820ec83aa" }, { "url": "https://git.kernel.org/stable/c/faea60deaa05c76f0772650f42eafde12bd39d93" }, { "url": "https://git.kernel.org/stable/c/07b71c342382b854ab8030b244aeab6a7228ad7d" }, { "url": "https://git.kernel.org/stable/c/4a69b83045d3195d5b9a9b053ad840ddb2998b4e" }, { "url": "https://git.kernel.org/stable/c/45ebb934ea50b436ce49b2f159f090dab0d7fa28" }, { "url": "https://git.kernel.org/stable/c/4d587cd8a72155089a627130bbd4716ec0856e21" } ], "title": "apparmor: mediate the implicit connect of TCP fast open sendmsg", "x_generator": { "engine": "bippy-1.2.0" } } } }