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CVE PROGRAM SOURCE RECORD9.8 Critical

CVE-2026-63984

ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress() ipv6_rpl_srh_decompress() computes: outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3); hdrlen is __u8. For n >= 127 the result exceeds 255 and silently truncates. With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16): (128 * 16) >> 3 = 256, truncated to 0 as __u8 The caller in ipv6_rpl_srh_rcv() then places the compressed header at buf + ((ohdr->hdrlen + 1) << 3). With hdrlen=0 this is buf + 8, but the decompressed region occupies buf[0..2055] (8-byte header plus 128 full addresses). The compressed header overlaps the decompressed data, and ipv6_rpl_srh_compress() writes into this overlap, corrupting the routing header of the forwarded packet. The existing guard at exthdrs.c:546 checks (n + 1) > 255, which prevents n+1 from overflowing unsigned char (the segments_left field), but does not prevent the computed hdrlen from overflowing __u8. n=127 passes because 128 <= 255, yet hdrlen=256 does not fit. Tighten the bound to (n + 1) > 127. This caps n at 126, giving hdrlen = (127 * 16) >> 3 = 254, which fits in __u8. The compressed header then lands at buf + ((254 + 1) << 3) = buf + 2040, exactly past the decompressed region (buf[0..2039]). No overlap. 127 segments is well beyond any realistic RPL deployment.

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 < 75b3680047bf09af8e7e471a7a6ddf2ce5847f56affected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < fd238c51b0fa5390cceca9f1ac5a9ffda8063eedaffected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < 3618b34942b76471d044369bfd30d58c39068bf1affected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < 97e06791368c01f0ad2a4b3269c2abe19485ca32affected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < de02fc049352af5a9595f015511222d0a85c326baffected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < 6fe1cb312038516cb4d9fa089d700af7059f1a64affected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < c0487a9c1e116cf349e2d1f302d9019670460858affected
  • 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < 9d5e7a46a9f6d8f503b41bfefef70659845f1679affected

Linux Linux

Default version status: affected

  • 5.7affected
  • 0 to < 5.7unaffected
  • 5.10.259 to ≤ 5.10.*unaffected
  • 5.15.210 to ≤ 5.15.*unaffected
  • 6.1.176 to ≤ 6.1.*unaffected
  • 6.6.143 to ≤ 6.6.*unaffected
  • 6.12.93 to ≤ 6.12.*unaffected
  • 6.18.35 to ≤ 6.18.*unaffected
  • 7.0.12 to ≤ 7.0.*unaffected
  • 7.1 to ≤ *unaffected

References