ipv6: rpl: reserve mac_len headroom when recompressed SRH grows_CVE-2026-43501

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: rpl: reserve mac_len headroom when recompressed SRH grows\n\nipv6_rpl_srh_rcv() decompresses an RFC 6554 Source Routing Header, swaps\nthe next segment into ipv6_hdr->daddr, recompresses, then pulls the old\nheader and pushes the new one plus the IPv6 header back.  The\nrecompressed header can be larger than the received one when the swap\nreduces the common-prefix length the segments share with daddr (CmprI=0,\nCmprE>0, seg[0][0] != daddr[0] gives the maximum +8 bytes).\n\npskb_expand_head() was gated on segments_left == 0, so on earlier\nsegments the push consumed unchecked headroom.  Once skb_push() leaves\nfewer than skb->mac_len bytes in front of data,\nskb_mac_header_rebuild()'s call to:\n\n\tskb_set_mac_header(skb, -skb->mac_len);\n\nwill store (data - head) - mac_len into the u16 mac_header field, which\nwraps to ~65530, and the following memmove() writes mac_len bytes ~64KiB\npast skb->head.\n\nA single AF_INET6/SOCK_RAW/IPV6_HDRINCL packet over lo with a two\nsegment type-3 SRH (CmprI=0, CmprE=15) reaches headroom 8 after one\npass; KASAN reports a 14-byte OOB write in ipv6_rthdr_rcv.\n\nFix this by expanding the head whenever the remaining room is less than\nthe push size plus mac_len, and request that much extra so the rebuilt\nMAC header fits afterwards.",
    "published": "2026-05-21T12:17:49.885Z",
    "modified": "2026-05-30T10:45:21.654Z",
    "type": "cve",
    "title": "ipv6: rpl: reserve mac_len headroom when recompressed SRH grows",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/8e8be63465a5e80394c70324603dfea1bfdad48f\nhttps://git.kernel.org/stable/c/4babc2d9fda2df43823b85d08a0180b68f1b0854\nhttps://git.kernel.org/stable/c/c261d07a80576dc8ccf394ef8f074f8c67a06b37\nhttps://git.kernel.org/stable/c/7398ebefbfd4f8a31d4f665a4213302fa995494b\nhttps://git.kernel.org/stable/c/9e6bf146b55999a095bb14f73a843942456d1adc",
    "id": "CVE-2026-43501",
    "bulletinFamily": "",
    "cwe": null,
    "cvelist": null,
    "sourceData": "Linux Linux 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\nLinux Linux 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\nLinux Linux 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\nLinux Linux 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\nLinux Linux 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\nLinux Linux 5.7",
    "sourceHref": "",
    "cvss": {
        "score": 9.8,
        "severity": "CRITICAL",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
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        "baseScore": 0,
        "baseSeverity": "",
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        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
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            "privilegesRequired": "",
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        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Linux",
    "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3",
    "vendor": "Linux",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
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    "ai_score": 0
}