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CVE-2026-63984

ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: total

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 · fixed in 75b3680047bf09af8e7e471a7a6ddf2ce5847f56; From 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 · fixed in fd238c51b0fa5390cceca9f1ac5a9ffda8063eed; From 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 · fixed in 3618b34942b76471d044369bfd30d58c39068bf1; From 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 · fixed in 97e06791368c01f0ad2a4b3269c2abe19485ca32; From 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 · fixed in de02fc049352af5a9595f015511222d0a85c326b; From 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 · fixed in 6fe1cb312038516cb4d9fa089d700af7059f1a64; From 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 · fixed in c0487a9c1e116cf349e2d1f302d9019670460858; From 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 · fixed in 9d5e7a46a9f6d8f503b41bfefef70659845f1679

  • Linux Linux

    5.7

  • KernelLinux

    From 5.7.0 · fixed in 5.10.259; From 5.11.0 · fixed in 5.15.210; From 5.16.0 · fixed in 6.1.176; From 6.2.0 · fixed in 6.6.143; From 6.7.0 · fixed in 6.12.93; From 6.13.0 · fixed in 6.18.35; From 6.19.0 · fixed in 7.0.12

References 8

git.kernel.org