{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-63867", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.017Z", "datePublished": "2026-07-19T14:18:37.234Z", "dateUpdated": "2026-07-20T13:41:01.328Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-07-20T13:41:01.328Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: close TOCTOU race while computing rcv_wnd\n\nThe MPTCP output path access locklessly the MPTCP-level ack_seq\nin multiple times, using possibly different values for the data_ack\nin the DSS option and to compute the announced rcv wnd for the same\npacket.\n\nRefactor the cote to avoid inconsistencies which may confuse the\npeer. Also ensure that the MPTCP level rcv wnd is updated only when\nthe egress packet actually contains a DSS ack."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H", "baseScore": 8.2, "baseSeverity": "HIGH"}}], "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": "fa3fe2b150316b294f2c662653501273ff25bba8", "lessThan": "301a33fd590c408a05c5df800e0cc1e6a8a2f8f8", "status": "affected", "versionType": "git"}, {"version": "fa3fe2b150316b294f2c662653501273ff25bba8", "lessThan": "68364963e5baf03f16b4420292291f75c8f66497", "status": "affected", "versionType": "git"}, {"version": "fa3fe2b150316b294f2c662653501273ff25bba8", "lessThan": "907ac6b1658e0277f979fcdfae2a753b495c1510", "status": "affected", "versionType": "git"}, {"version": "fa3fe2b150316b294f2c662653501273ff25bba8", "lessThan": "c4f4cf60797974873dbc8e100144682a6f2f861f", "status": "affected", "versionType": "git"}, {"version": "fa3fe2b150316b294f2c662653501273ff25bba8", "lessThan": "3b8cbba7c0ed31189c89f90be247b8973ffa79ef", "status": "affected", "versionType": "git"}, {"version": "fa3fe2b150316b294f2c662653501273ff25bba8", "lessThan": "8f4f0a157e8436a05bf8c3670b24dbc258911c43", "status": "affected", "versionType": "git"}, {"version": "fa3fe2b150316b294f2c662653501273ff25bba8", "lessThan": "8ab24fdebc369c0dfb90f82c1650b1e66662bb45", "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": "5.11", "status": "affected"}, {"version": "0", "lessThan": "5.11", "status": "unaffected", "versionType": "semver"}, {"version": "5.15.210", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.176", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.143", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.94", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.36", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.0.13", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.1", "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": "5.11", "versionEndExcluding": "5.15.210"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "6.1.176"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "6.6.143"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "6.12.94"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "6.18.36"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "7.0.13"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "7.1"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/301a33fd590c408a05c5df800e0cc1e6a8a2f8f8"}, {"url": "https://git.kernel.org/stable/c/68364963e5baf03f16b4420292291f75c8f66497"}, {"url": "https://git.kernel.org/stable/c/907ac6b1658e0277f979fcdfae2a753b495c1510"}, {"url": "https://git.kernel.org/stable/c/c4f4cf60797974873dbc8e100144682a6f2f861f"}, {"url": "https://git.kernel.org/stable/c/3b8cbba7c0ed31189c89f90be247b8973ffa79ef"}, {"url": "https://git.kernel.org/stable/c/8f4f0a157e8436a05bf8c3670b24dbc258911c43"}, {"url": "https://git.kernel.org/stable/c/8ab24fdebc369c0dfb90f82c1650b1e66662bb45"}], "title": "mptcp: close TOCTOU race while computing rcv_wnd", "x_generator": {"engine": "bippy-1.2.0"}}}}

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{}

{"bugzilla": {"description": "kernel: mptcp: close TOCTOU race while computing rcv_wnd", "id": "2502304", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2502304"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-367", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nmptcp: close TOCTOU race while computing rcv_wnd\nThe MPTCP output path access locklessly the MPTCP-level ack_seq\nin multiple times, using possibly different values for the data_ack\nin the DSS option and to compute the announced rcv wnd for the same\npacket.\nRefactor the cote to avoid inconsistencies which may confuse the\npeer. Also ensure that the MPTCP level rcv wnd is updated only when\nthe egress packet actually contains a DSS ack.", "A flaw was found in the Linux kernel's Multipath TCP (MPTCP) implementation. A race condition exists when computing the receive window, where the acknowledgment sequence number is accessed without proper locking. This can lead to inconsistencies in how the receive window is calculated and communicated to a peer, potentially causing connection instability or disruption."], "name": "CVE-2026-63867", "package_state": [{"cpe": "cpe:/a:redhat:hummingbird:1", "fix_state": "Not affected", "impact": "important", "package_name": "erlang27", "product_name": "Red Hat Hardened Images"}], "public_date": "2026-07-19T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-63867\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-63867\nhttps://lore.kernel.org/linux-cve-announce/2026071912-CVE-2026-63867-eac1@gregkh/T"], "threat_severity": "Moderate"}

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