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CVE PROGRAM SOURCE RECORD9.8 Critical

CVE-2026-43501

ipv6: rpl: reserve mac_len headroom when recompressed SRH grows

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Status
Published
Published
Updated
Assigning organization
Linux

Description

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < bde199c72d319a4e207f88daabc888317504e2fbaffected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < be1fa0aa9b4fdd5a8b7a61ba520a690a68391e6eaffected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < 0a9e8053f1f8a8e1bfc1dd61ffe67be6c1180402affected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < 8e8be63465a5e80394c70324603dfea1bfdad48faffected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < 4babc2d9fda2df43823b85d08a0180b68f1b0854affected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < c261d07a80576dc8ccf394ef8f074f8c67a06b37affected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < 7398ebefbfd4f8a31d4f665a4213302fa995494baffected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < 9e6bf146b55999a095bb14f73a843942456d1adcaffected

Linux Linux

Default version status: affected

  • 5.7affected
  • 0 to < 5.7unaffected
  • 5.10.258 to ≤ 5.10.*unaffected
  • 5.15.209 to ≤ 5.15.*unaffected
  • 6.1.175 to ≤ 6.1.*unaffected
  • 6.6.140 to ≤ 6.6.*unaffected
  • 6.12.86 to ≤ 6.12.*unaffected
  • 6.18.27 to ≤ 6.18.*unaffected
  • 7.0.4 to ≤ 7.0.*unaffected
  • 7.1 to ≤ *unaffected

References