{"api_version":"1","generated_at":"2026-05-06T17:16:30+00:00","cve":"CVE-2026-43254","urls":{"html":"https://cve.report/CVE-2026-43254","api":"https://cve.report/api/cve/CVE-2026-43254.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-43254","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-43254"},"summary":{"title":"ovpn: tcp - fix packet extraction from stream","description":"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%.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-05-06 12:16:46","updated_at":"2026-05-06 13:07:51"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/d4f687fbbce45b5e88438e89b5e26c0c15847992","name":"https://git.kernel.org/stable/c/d4f687fbbce45b5e88438e89b5e26c0c15847992","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/7dba6cd7fb168d7615194a631c9c100c1c224131","name":"https://git.kernel.org/stable/c/7dba6cd7fb168d7615194a631c9c100c1c224131","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/0315bec883c67fa1413c61e504a28dc5bd02eb37","name":"https://git.kernel.org/stable/c/0315bec883c67fa1413c61e504a28dc5bd02eb37","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-43254","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43254","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 11851cbd60ea1e5abbd97619d69845ead99303d6 0315bec883c67fa1413c61e504a28dc5bd02eb37 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 11851cbd60ea1e5abbd97619d69845ead99303d6 7dba6cd7fb168d7615194a631c9c100c1c224131 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 11851cbd60ea1e5abbd97619d69845ead99303d6 d4f687fbbce45b5e88438e89b5e26c0c15847992 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.16","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.16 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.16 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.19.6 6.19.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"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"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.16","versionStartIncluding":"6.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.19.6","versionStartIncluding":"6.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0","versionStartIncluding":"6.16","vulnerable":true}],"negate":false,"operator":"OR"}]}],"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%."}],"providerMetadata":{"dateUpdated":"2026-05-06T11:28:43.871Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"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"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-43254","datePublished":"2026-05-06T11:28:43.871Z","dateReserved":"2026-05-01T14:12:55.996Z","dateUpdated":"2026-05-06T11:28:43.871Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-05-06 12:16:46","lastModifiedDate":"2026-05-06 13:07:51","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"43254","Ordinal":"1","Title":"ovpn: tcp - fix packet extraction from stream","CVE":"CVE-2026-43254","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"43254","Ordinal":"1","NoteData":"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%.","Type":"Description","Title":"ovpn: tcp - fix packet extraction from stream"}]}}}