Answer in brief
CVE-2026-63984 records a Critical severity (CVSS 9.8) vulnerability in ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress(). The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <75b3680047bf09af8e7e471a7a6ddf2ce5847f56 || >=8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <fd238c51b0fa5390cceca9f1ac5a9ffda8063eed || >=8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <3618b34942b76471d044369bfd30d58c39068bf1 || >=8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <97e06791368c01f0ad2a4b3269c2abe19485ca32 || >=8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <de02fc049352af5a9595f015511222d0a85c326b || >=8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <6fe1cb312038516cb4d9fa089d700af7059f1a64 || >=8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <c0487a9c1e116cf349e2d1f302d9019670460858 || >=8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 <9d5e7a46a9f6d8f503b41bfefef70659845f1679 | 75b3680047bf09af8e7e471a7a6ddf2ce5847f56, fd238c51b0fa5390cceca9f1ac5a9ffda8063eed, 3618b34942b76471d044369bfd30d58c39068bf1, 97e06791368c01f0ad2a4b3269c2abe19485ca32, de02fc049352af5a9595f015511222d0a85c326b, 6fe1cb312038516cb4d9fa089d700af7059f1a64, c0487a9c1e116cf349e2d1f302d9019670460858, 9d5e7a46a9f6d8f503b41bfefef70659845f1679 |
| Linux/Linuxgeneric | 5.7 | Not reported |
Published upstream
Jul 19, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 19, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
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.
Quoted source text, attributed separately from HOL analysis.