CVE-2026-43254

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-43254", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-05-01T14:12:55.996Z", "datePublished": "2026-05-06T11:28:43.871Z", "dateUpdated": "2026-08-05T12:26:54.790Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:26:54.790Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\novpn: tcp - fix packet extraction from stream\n\nWhen processing TCP stream data in ovpn_tcp_recv, we receive large\ncloned skbs from __strp_rcv that may contain multiple coalesced packets.\nThe current implementation has two bugs:\n\n1. Header offset overflow: Using pskb_pull with large offsets on\n coalesced skbs causes skb->data - skb->head to exceed the u16 storage\n of skb->network_header. This causes skb_reset_network_header to fail\n on the inner decapsulated packet, resulting in packet drops.\n\n2. Unaligned protocol headers: Extracting packets from arbitrary\n positions within the coalesced TCP stream provides no alignment\n guarantees for the packet data causing performance penalties on\n architectures without efficient unaligned access. Additionally,\n openvpn's 2-byte length prefix on TCP packets causes the subsequent\n 4-byte opcode and packet ID fields to be inherently misaligned.\n\nFix both issues by allocating a new skb for each openvpn packet and\nusing skb_copy_bits to extract only the packet content into the new\nbuffer, skipping the 2-byte length prefix. Also, check the length before\ninvoking the function that performs the allocation to avoid creating an\ninvalid skb.\n\nIf the packet has to be forwarded to userspace the 2-byte prefix can be\npushed to the head safely, without misalignment.\n\nAs a side effect, this approach also avoids the expensive linearization\nthat pskb_pull triggers on cloned skbs with page fragments. In testing,\nthis resulted in TCP throughput improvements of up to 74%."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:N - The vulnerable parser is reached by TCP stream data received from a remote OpenVPN peer over the network.\nAC:L - The attacker controls the TCP byte stream and OpenVPN length-prefixed records; no race or condition outside attacker control is required.\nPR:N - Local CAP_NET_ADMIN is needed only to configure the ovpn device and attach the socket, not to send the triggering network data once the service is exposed.\nUI:N - No victim user action is needed beyond the already-running OpenVPN TCP deployment.\nS:U - The impact remains within the kernel/OpenVPN networking security authority and does not cross a VM, sandbox, or hardware isolation boundary.\nC:N - The traced path leads to packet extraction/header-offset failure and drops, with no demonstrated kernel memory disclosure primitive.\nI:N - The bug corrupts skb parsing state/alignment but does not provide a demonstrated ability to modify kernel memory or protected data.\nA:H - A remote sender can repeatedly trigger packet drops in the ovpn TCP data path, and on strict-alignment systems the unaligned kernel accesses can severely disrupt or crash the data channel."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["drivers/net/ovpn/tcp.c"], "versions": [{"version": "11851cbd60ea1e5abbd97619d69845ead99303d6", "lessThan": "0315bec883c67fa1413c61e504a28dc5bd02eb37", "status": "affected", "versionType": "git"}, {"version": "11851cbd60ea1e5abbd97619d69845ead99303d6", "lessThan": "7dba6cd7fb168d7615194a631c9c100c1c224131", "status": "affected", "versionType": "git"}, {"version": "11851cbd60ea1e5abbd97619d69845ead99303d6", "lessThan": "d4f687fbbce45b5e88438e89b5e26c0c15847992", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["drivers/net/ovpn/tcp.c"], "versions": [{"version": "6.16", "status": "affected"}, {"version": "0", "lessThan": "6.16", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.16", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.19.6", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.0", "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": "6.16", "versionEndExcluding": "6.18.16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "6.19.6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "7.0"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/0315bec883c67fa1413c61e504a28dc5bd02eb37"}, {"url": "https://git.kernel.org/stable/c/7dba6cd7fb168d7615194a631c9c100c1c224131"}, {"url": "https://git.kernel.org/stable/c/d4f687fbbce45b5e88438e89b5e26c0c15847992"}], "title": "ovpn: tcp - fix packet extraction from stream", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["drivers/net/ovpn/tcp.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "0315bec883c67fa1413c61e504a28dc5bd02eb37", "status": "affected", "version": "11851cbd60ea1e5abbd97619d69845ead99303d6", "versionType": "git"}, {"lessThan": "7dba6cd7fb168d7615194a631c9c100c1c224131", "status": "affected", "version": "11851cbd60ea1e5abbd97619d69845ead99303d6", "versionType": "git"}, {"lessThan": "d4f687fbbce45b5e88438e89b5e26c0c15847992", "status": "affected", "version": "11851cbd60ea1e5abbd97619d69845ead99303d6", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["drivers/net/ovpn/tcp.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "6.16"}, {"lessThan": "6.16", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.16", "versionType": "semver"}, {"lessThanOrEqual": "6.19.*", "status": "unaffected", "version": "6.19.6", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.0", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "B4562EDA-AFEA-4C62-97CC-C83E109A5F19", "versionEndExcluding": "6.18.16", "versionStartIncluding": "6.16", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "373EEEDA-FAA1-4FB4-B6ED-DB4DD99DBE67", "versionEndExcluding": "6.19.6", "versionStartIncluding": "6.19", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\novpn: tcp - fix packet extraction from stream\n\nWhen processing TCP stream data in ovpn_tcp_recv, we receive large\ncloned skbs from __strp_rcv that may contain multiple coalesced packets.\nThe current implementation has two bugs:\n\n1. Header offset overflow: Using pskb_pull with large offsets on\n coalesced skbs causes skb->data - skb->head to exceed the u16 storage\n of skb->network_header. This causes skb_reset_network_header to fail\n on the inner decapsulated packet, resulting in packet drops.\n\n2. Unaligned protocol headers: Extracting packets from arbitrary\n positions within the coalesced TCP stream provides no alignment\n guarantees for the packet data causing performance penalties on\n architectures without efficient unaligned access. Additionally,\n openvpn's 2-byte length prefix on TCP packets causes the subsequent\n 4-byte opcode and packet ID fields to be inherently misaligned.\n\nFix both issues by allocating a new skb for each openvpn packet and\nusing skb_copy_bits to extract only the packet content into the new\nbuffer, skipping the 2-byte length prefix. Also, check the length before\ninvoking the function that performs the allocation to avoid creating an\ninvalid skb.\n\nIf the packet has to be forwarded to userspace the 2-byte prefix can be\npushed to the head safely, without misalignment.\n\nAs a side effect, this approach also avoids the expensive linearization\nthat pskb_pull triggers on cloned skbs with page fragments. In testing,\nthis resulted in TCP throughput improvements of up to 74%."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\novpn: tcp - corrige la extracci\u00f3n de paquetes del flujo\n\nAl procesar datos de flujo TCP en ovpn_tcp_recv, recibimos skbs clonados grandes de __strp_rcv que pueden contener m\u00faltiples paquetes fusionados. La implementaci\u00f3n actual tiene dos errores:\n\n1. Desbordamiento de desplazamiento de cabecera: Usar pskb_pull con grandes desplazamientos en skbs fusionados hace que skb -> data - skb -> head exceda el almacenamiento u16 de skb -> network_header. Esto hace que skb_reset_network_header falle en el paquete interno desencapsulado, lo que resulta en p\u00e9rdidas de paquetes.\n\n2. Cabeceras de protocolo no alineadas: Extraer paquetes de posiciones arbitrarias dentro del flujo TCP fusionado no proporciona garant\u00edas de alineaci\u00f3n para los datos del paquete, causando penalizaciones de rendimiento en arquitecturas sin acceso no alineado eficiente. Adem\u00e1s, el prefijo de longitud de 2 bytes de openvpn en los paquetes TCP hace que los campos subsiguientes de c\u00f3digo de operaci\u00f3n de 4 bytes e ID de paquete est\u00e9n inherentemente desalineados.\n\nSoluciona ambos problemas asignando un nuevo skb para cada paquete openvpn y usando skb_copy_bits para extraer solo el contenido del paquete en el nuevo b\u00fafer, omitiendo el prefijo de longitud de 2 bytes. Adem\u00e1s, verifica la longitud antes de invocar la funci\u00f3n que realiza la asignaci\u00f3n para evitar crear un skb inv\u00e1lido.\n\nSi el paquete tiene que ser reenviado al espacio de usuario, el prefijo de 2 bytes puede ser empujado a la cabecera de forma segura, sin desalineaci\u00f3n.\n\nComo efecto secundario, este enfoque tambi\u00e9n evita la costosa linealizaci\u00f3n que pskb_pull desencadena en skbs clonados con fragmentos de p\u00e1gina. En las pruebas, esto result\u00f3 en mejoras de rendimiento TCP de hasta el 74%."}], "id": "CVE-2026-43254", "lastModified": "2026-11-11T20:10:00.273", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}]}, "published": "2026-05-06T12:16:46.143", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/0315bec883c67fa1413c61e504a28dc5bd02eb37"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/7dba6cd7fb168d7615194a631c9c100c1c224131"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d4f687fbbce45b5e88438e89b5e26c0c15847992"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-190"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: ovpn: tcp - fix packet extraction from stream", "id": "2467175", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2467175"}, "csaw": false, "cwe": "CWE-190", "details": ["A flaw was found in the Linux kernel's handling of OpenVPN (ovpn) TCP network traffic. This vulnerability occurs when the kernel processes multiple network packets that have been combined into a single stream. An attacker could exploit this by sending specially crafted TCP packets, leading to issues such as dropped packets and reduced network performance, effectively causing a denial of service."], "name": "CVE-2026-43254", "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"}], "public_date": "2026-05-06T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-43254\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-43254\nhttps://lore.kernel.org/linux-cve-announce/2026050604-CVE-2026-43254-1146@gregkh/T"]}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[11851cbd60ea1e5abbd97619d69845ead99303d6,0315bec883c67fa1413c61e504a28dc5bd02eb37)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[11851cbd60ea1e5abbd97619d69845ead99303d6,7dba6cd7fb168d7615194a631c9c100c1c224131)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[11851cbd60ea1e5abbd97619d69845ead99303d6,d4f687fbbce45b5e88438e89b5e26c0c15847992)"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"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": "6.16"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[0,6.16)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.18.16,6.19.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.19.6,6.20.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[7.0,*]"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}], "created": "2026-05-06T16:15:06.983002+00:00", "title": "OpenVPN TCP Packet Processing Vulnerability Causing Packet Loss and Performance Degradation", "updated": "2026-05-08T20:15:15.769060+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}