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CVE-2026-43501

ipv6: rpl: reserve mac_len headroom when recompressed SRH grows

CRITICAL 9.8

At a glance

Source
NVD
EPSS
EPSS 0.73 % · percentile 54 ()
State
PUBLISHED
Published
Updated
Assigner
Linux
NVD status
Modified

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.

Weaknesses (CWE)

  • CWE-131 — Incorrect Calculation of Buffer Size
  • CWE-787 — Out-of-bounds Write

References

Scores

VersionScoreVectorScored by
CVSS 3.1CRITICAL 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HLinux
CVSS 3.1HIGH 7.5CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:Hredhat-SADP
CVSS 3.1CRITICAL 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HNVD · 416baaa9-dc9f-4396-8d5f-8c081fb06d67 (Secondary)
CVSS 3.1HIGH 7.5CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HNVD · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c (Secondary)

European references

CERT-FR advisories

Affected configurations (NVD CPE)

Affected products

ProductVersions
Linux · Linuxaffected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < bde199c72d319a4e207f88daabc888317504e2fb ; affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < be1fa0aa9b4fdd5a8b7a61ba520a690a68391e6e ; affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < 0a9e8053f1f8a8e1bfc1dd61ffe67be6c1180402 ; affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < 8e8be63465a5e80394c70324603dfea1bfdad48f ; affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < 4babc2d9fda2df43823b85d08a0180b68f1b0854 ; affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 < c261d07a80576dc8ccf394ef8f074f8c67a06b37
Linux · Linuxaffected 5.7 ; unaffected 0 < 5.7 ; unaffected 5.10.258 ≤ 5.10.* ; unaffected 5.15.209 ≤ 5.15.* ; unaffected 6.1.175 ≤ 6.1.* ; unaffected 6.6.140 ≤ 6.6.*

Sources

SourceLicence
CVE List (CVEProject cvelistV5)CVE Program Terms of Use
EPSS (FIRST.org)FIRST — attribution requested
ENISA EUVDENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feedsPublic domain — this product uses data from the NVD API but is not endorsed or certified by the NVD