ovpn: tcp – fix packet extraction from stream_CVE-2026-43254

{
    "lastseen": "",
    "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%.",
    "published": "2026-05-06T11:28:43.871Z",
    "modified": "2026-05-08T12:41:37.366Z",
    "type": "cve",
    "title": "ovpn: tcp - fix packet extraction from stream",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/0315bec883c67fa1413c61e504a28dc5bd02eb37\nhttps://git.kernel.org/stable/c/7dba6cd7fb168d7615194a631c9c100c1c224131\nhttps://git.kernel.org/stable/c/d4f687fbbce45b5e88438e89b5e26c0c15847992",
    "id": "CVE-2026-43254",
    "bulletinFamily": "",
    "cwe": null,
    "cvelist": null,
    "sourceData": "Linux Linux 11851cbd60ea1e5abbd97619d69845ead99303d6\nLinux Linux 11851cbd60ea1e5abbd97619d69845ead99303d6\nLinux Linux 11851cbd60ea1e5abbd97619d69845ead99303d6\nLinux Linux 6.16",
    "sourceHref": "",
    "cvss": {
        "score": 7.5,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
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            "privilegesRequired": "",
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            "confidentialityImpact": "",
            "integrityImpact": "",
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        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Linux",
    "version": "11851cbd60ea1e5abbd97619d69845ead99303d6",
    "vendor": "Linux",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
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    "ai_score": 0
}