ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63984
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:17 UTC
Updated2026-07-20 15:17:00 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.001760000 probability, percentile 0.073880000 (date 2026-07-20)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 75b3680047bf09af8e7e471a7a6ddf2ce5847f56 git Not specified
CNA Linux Linux affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 fd238c51b0fa5390cceca9f1ac5a9ffda8063eed git Not specified
CNA Linux Linux affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 3618b34942b76471d044369bfd30d58c39068bf1 git Not specified
CNA Linux Linux affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 97e06791368c01f0ad2a4b3269c2abe19485ca32 git Not specified
CNA Linux Linux affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 de02fc049352af5a9595f015511222d0a85c326b git Not specified
CNA Linux Linux affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 6fe1cb312038516cb4d9fa089d700af7059f1a64 git Not specified
CNA Linux Linux affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 c0487a9c1e116cf349e2d1f302d9019670460858 git Not specified
CNA Linux Linux affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 9d5e7a46a9f6d8f503b41bfefef70659845f1679 git Not specified
CNA Linux Linux affected 5.7 Not specified
CNA Linux Linux unaffected 5.7 semver Not specified
CNA Linux Linux unaffected 5.10.259 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.210 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.176 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.143 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.93 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.35 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.12 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/6fe1cb312038516cb4d9fa089d700af7059f1a64 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c0487a9c1e116cf349e2d1f302d9019670460858 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/97e06791368c01f0ad2a4b3269c2abe19485ca32 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/75b3680047bf09af8e7e471a7a6ddf2ce5847f56 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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