CVE-2026-43501 (GCVE-0-2026-43501)

Vulnerability from cvelistv5 – Published: 2026-05-21 12:17 – Updated: 2026-05-21 12:17
VLAI?
Title
ipv6: rpl: reserve mac_len headroom when recompressed SRH grows
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: rpl: reserve mac_len headroom when recompressed SRH grows ipv6_rpl_srh_rcv() decompresses an RFC 6554 Source Routing Header, swaps the next segment into ipv6_hdr->daddr, recompresses, then pulls the old header and pushes the new one plus the IPv6 header back. The recompressed header can be larger than the received one when the swap reduces the common-prefix length the segments share with daddr (CmprI=0, CmprE>0, seg[0][0] != daddr[0] gives the maximum +8 bytes). pskb_expand_head() was gated on segments_left == 0, so on earlier segments the push consumed unchecked headroom. Once skb_push() leaves fewer than skb->mac_len bytes in front of data, skb_mac_header_rebuild()'s call to: skb_set_mac_header(skb, -skb->mac_len); will store (data - head) - mac_len into the u16 mac_header field, which wraps to ~65530, and the following memmove() writes mac_len bytes ~64KiB past skb->head. A single AF_INET6/SOCK_RAW/IPV6_HDRINCL packet over lo with a two segment type-3 SRH (CmprI=0, CmprE=15) reaches headroom 8 after one pass; KASAN reports a 14-byte OOB write in ipv6_rthdr_rcv. Fix this by expanding the head whenever the remaining room is less than the push size plus mac_len, and request that much extra so the rebuilt MAC header fits afterwards.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < 8e8be63465a5e80394c70324603dfea1bfdad48f (git)
Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < 4babc2d9fda2df43823b85d08a0180b68f1b0854 (git)
Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < c261d07a80576dc8ccf394ef8f074f8c67a06b37 (git)
Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < 7398ebefbfd4f8a31d4f665a4213302fa995494b (git)
Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < 9e6bf146b55999a095bb14f73a843942456d1adc (git)
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Linux Linux Affected: 5.7
Unaffected: 0 , < 5.7 (semver)
Unaffected: 6.6.140 , ≤ 6.6.* (semver)
Unaffected: 6.12.86 , ≤ 6.12.* (semver)
Unaffected: 6.18.27 , ≤ 6.18.* (semver)
Unaffected: 7.0.4 , ≤ 7.0.* (semver)
Unaffected: 7.1-rc2 , ≤ * (original_commit_for_fix)
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{
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/exthdrs.c"
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          "value": "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-\u003edaddr, 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\u003e0, 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-\u003emac_len bytes in front of data,\nskb_mac_header_rebuild()\u0027s call to:\n\n\tskb_set_mac_header(skb, -skb-\u003emac_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-\u003ehead.\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."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-05-21T12:17:49.885Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        {
          "url": "https://git.kernel.org/stable/c/9e6bf146b55999a095bb14f73a843942456d1adc"
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    "cveId": "CVE-2026-43501",
    "datePublished": "2026-05-21T12:17:49.885Z",
    "dateReserved": "2026-05-01T14:12:56.014Z",
    "dateUpdated": "2026-05-21T12:17:49.885Z",
    "state": "PUBLISHED"
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  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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