{ "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" } } } }