CVE-2026-99042

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-99042", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.387Z", "datePublished": "2026-10-23T12:22:01.804Z", "dateUpdated": "2026-10-24T14:10:09.161Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-24T14:10:09.161Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6\n\nio_connect_bpf_populate() fills connect.port and connect.v6_addr for\nAF_INET6 only when addr_len >= sizeof(struct sockaddr_in6), i.e. 28\nbytes.\n\nThe IPv6 connect paths accept SIN6_LEN_RFC2133 (24 bytes), which\nalready holds sin6_port and sin6_addr. io_connect() passes addr_len to\nthe socket layer unchanged.\n\nAt addr_len 24 the filter sees family AF_INET6 with port and address\nzero, while the kernel connects to the real destination. A filter that\ndenies an IPv6 port or address is bypassed. Denying connect.port == P\nrejects [::1]:P with -EACCES at addr_len 28 but connects at addr_len 24.\n\nUse SIN6_LEN_RFC2133 as the threshold. sin6_scope_id stays zero when\nabsent.\n\nThe threshold mismatch was found by an AI coding assistant (Claude Code)\ncomparing this hook against the net/ipv6 length checks on my\ninstructions; it also drafted the reproducer and this patch. I verified\nthe bypass and the fix in a VM on 7.3-rc6 and that 7.2 has the same\ncode."}], "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 - An attacker reaches the patched io_connect_bpf_populate() by locally submitting IORING_OP_CONNECT through io_uring_enter(), with sqe->addr2 supplying the malicious 24-byte length. No network packet carries the value creating the mismatch.\nAC:L - Against a CONNECT filter denying an IPv6 port or address, addr2=24 deterministically makes io_connect_bpf_populate() expose zero port/address while tcp_v6_connect() accepts and uses the real fields; no race or uncontrolled condition is involved.\nPR:L - No capability check exists in io_uring_enter(), io_connect_prep(), or io_connect(), and AF_INET6 SOCK_STREAM creation avoids inet6_create()'s CAP_NET_RAW check. An ordinary confined process with access to the filtered ring can trigger the bypass.\nUI:N - The confined process prepares and submits the 24-byte sockaddr itself, and io_connect_prep() copies it during io_uring_enter(); no other user must mount, open, approve, or otherwise act.\nS:C - The false port/address view escapes the io_uring BPF CONNECT sandbox: __io_uring_run_bpf_filters() allows an operation that an inherited or ring-level filter intended to deny, reaching network resources outside that policy scope.\nC:H - After the filter sees :: and port 0, tcp_v6_connect() uses sin6_addr and sin6_port from the same 24 bytes; the confined process can establish a full socket and read responses from IPv6 services the CONNECT filter explicitly made inaccessible.\nI:H - tcp_v6_connect() stores the hidden destination in sk_v6_daddr and inet_dport and establishes the denied socket, enabling arbitrary application data and requests to be sent to IPv6 services and ports prohibited by the sandbox policy.\nA:N - The bug only substitutes zero values in the filter context; move_addr_to_kernel() safely copies 24 bytes and the IPv6 socket layer accepts that size. It introduces no corruption, out-of-bounds access, oops, hang, or resource exhaustion."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["io_uring/net.c"], "versions": [{"version": "899bea8248cee35d54760a5e7d61a76af8e64411", "lessThan": "596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5", "status": "affected", "versionType": "git"}, {"version": "899bea8248cee35d54760a5e7d61a76af8e64411", "lessThan": "aa5d5f8e502318e783545ba5d04bb40130b83e20", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["io_uring/net.c"], "versions": [{"version": "7.2", "status": "affected"}, {"version": "0", "lessThan": "7.2", "status": "unaffected", "versionType": "semver"}, {"version": "7.2.11", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.3", "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": "7.2", "versionEndExcluding": "7.2.11"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.2", "versionEndExcluding": "7.3"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5"}, {"url": "https://git.kernel.org/stable/c/aa5d5f8e502318e783545ba5d04bb40130b83e20"}], "title": "io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["io_uring/net.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5", "status": "affected", "version": "899bea8248cee35d54760a5e7d61a76af8e64411", "versionType": "git"}, {"lessThan": "aa5d5f8e502318e783545ba5d04bb40130b83e20", "status": "affected", "version": "899bea8248cee35d54760a5e7d61a76af8e64411", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["io_uring/net.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "7.2"}, {"lessThan": "7.2", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "7.2.*", "status": "unaffected", "version": "7.2.11", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.3", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6\n\nio_connect_bpf_populate() fills connect.port and connect.v6_addr for\nAF_INET6 only when addr_len >= sizeof(struct sockaddr_in6), i.e. 28\nbytes.\n\nThe IPv6 connect paths accept SIN6_LEN_RFC2133 (24 bytes), which\nalready holds sin6_port and sin6_addr. io_connect() passes addr_len to\nthe socket layer unchanged.\n\nAt addr_len 24 the filter sees family AF_INET6 with port and address\nzero, while the kernel connects to the real destination. A filter that\ndenies an IPv6 port or address is bypassed. Denying connect.port == P\nrejects [::1]:P with -EACCES at addr_len 28 but connects at addr_len 24.\n\nUse SIN6_LEN_RFC2133 as the threshold. sin6_scope_id stays zero when\nabsent.\n\nThe threshold mismatch was found by an AI coding assistant (Claude Code)\ncomparing this hook against the net/ipv6 length checks on my\ninstructions; it also drafted the reproducer and this patch. I verified\nthe bypass and the fix in a VM on 7.3-rc6 and that 7.2 has the same\ncode."}], "id": "CVE-2026-99042", "lastModified": "2026-10-24T14:16:53.347", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "NONE", "baseScore": 8.4, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N", "version": "3.1"}, "exploitabilityScore": 2.0, "impactScore": 5.8, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}]}, "published": "2026-10-23T13:17:27.610", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/aa5d5f8e502318e783545ba5d04bb40130b83e20"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{"bugzilla": {"description": "kernel: io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6", "id": "2559692", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2559692"}, "csaw": false, "cvss3": {"cvss3_base_score": "4.4", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N", "status": "draft"}, "cwe": "CWE-807", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nio_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6\nio_connect_bpf_populate() fills connect.port and connect.v6_addr for\nAF_INET6 only when addr_len >= sizeof(struct sockaddr_in6), i.e. 28\nbytes.\nThe IPv6 connect paths accept SIN6_LEN_RFC2133 (24 bytes), which\nalready holds sin6_port and sin6_addr. io_connect() passes addr_len to\nthe socket layer unchanged.\nAt addr_len 24 the filter sees family AF_INET6 with port and address\nzero, while the kernel connects to the real destination. A filter that\ndenies an IPv6 port or address is bypassed. Denying connect.port == P\nrejects [::1]:P with -EACCES at addr_len 28 but connects at addr_len 24.\nUse SIN6_LEN_RFC2133 as the threshold. sin6_scope_id stays zero when\nabsent.\nThe threshold mismatch was found by an AI coding assistant (Claude Code)\ncomparing this hook against the net/ipv6 length checks on my\ninstructions; it also drafted the reproducer and this patch. I verified\nthe bypass and the fix in a VM on 7.3-rc6 and that 7.2 has the same\ncode.", "A flaw was found in the Linux kernel's io_uring subsystem. When evaluating IPv6 network connections, security filters are supplied with zeroed address and port values if a caller provides a valid 24-byte address structure instead of the full 28-byte structure. A local attacker can exploit this flaw by submitting connection requests with shorter address lengths to bypass Berkeley Packet Filter (BPF) network security rules and connect to restricted destinations."], "name": "CVE-2026-99042", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Not affected", "package_name": "openshift/ose-rhel-coreos-8", "product_name": "Red Hat OpenShift Container Platform 4"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Not affected", "package_name": "openshift/ose-rhel-coreos-9", "product_name": "Red Hat OpenShift Container Platform 4"}], "public_date": "2026-10-23T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-99042\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-99042\nhttps://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-99042.mbox"], "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[899bea8248cee35d54760a5e7d61a76af8e64411,596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[899bea8248cee35d54760a5e7d61a76af8e64411,aa5d5f8e502318e783545ba5d04bb40130b83e20)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "7.2"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[0,7.2)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[7.2.11,7.3.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[7.3,*]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[899bea8248cee35d54760a5e7d61a76af8e64411,596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[899bea8248cee35d54760a5e7d61a76af8e64411,aa5d5f8e502318e783545ba5d04bb40130b83e20)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "7.2"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[0,7.2)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[7.2.11,7.3.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[7.3,*]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}], "created": "2026-10-23T17:00:15.614323+00:00", "updated": "2026-10-29T15:00:22.045451+00:00", "vendors": ["linux", "linux$PRODUCT$linux", "linux$PRODUCT$linux_kernel"], "weaknesses": ["CWE-20", "CWE-807"]}