CVE-2026-63984
CVE CVE-2026-63984EUVD EUVD-2026-45757Published 2026-07-19T14:56:06.000ZLast changed 2026-08-05T12:37:52.000ZCVSS 9.8
What the advisory describes
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.
Source: EUVD (ENISA), in the words of the advisory.
Products the advisory names
These come from the advisory itself, not from any check we performed.
- Linux — Linux 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <c0487a9c1e116cf349e2d1f302d9019670460858; patch: 5.10.259; 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <de02fc049352af5a9595f015511222d0a85c326b; patch: 6.6.143; patch: 6.12.93; 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <3618b34942b76471d044369bfd30d58c39068bf1; 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <75b3680047bf09af8e7e471a7a6ddf2ce5847f56; patch: 0; patch: 7.0.12; patch: 7.1; patch: 5.15.210; patch: 6.1.176; 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <9d5e7a46a9f6d8f503b41bfefef70659845f1679; 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <fd238c51b0fa5390cceca9f1ac5a9ffda8063eed; 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <97e06791368c01f0ad2a4b3269c2abe19485ca32; 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <6fe1cb312038516cb4d9fa089d700af7059f1a64; patch: 6.18.35; 5.7
The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.
Carried in the product catalogue
An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.
- Linux — Linux
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