CVE-2026-63984 (GCVE-0-2026-63984)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:56 – Updated: 2026-07-20 13:42
VLAI
Title
ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()
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.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < 75b3680047bf09af8e7e471a7a6ddf2ce5847f56 (git)
Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < fd238c51b0fa5390cceca9f1ac5a9ffda8063eed (git)
Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < 3618b34942b76471d044369bfd30d58c39068bf1 (git)
Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < 97e06791368c01f0ad2a4b3269c2abe19485ca32 (git)
Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < de02fc049352af5a9595f015511222d0a85c326b (git)
Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < 6fe1cb312038516cb4d9fa089d700af7059f1a64 (git)
Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < c0487a9c1e116cf349e2d1f302d9019670460858 (git)
Affected: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 , < 9d5e7a46a9f6d8f503b41bfefef70659845f1679 (git)
Create a notification for this product.
Linux Linux Affected: 5.7
Unaffected: 0 , < 5.7 (semver)
Unaffected: 5.10.259 , ≤ 5.10.* (semver)
Unaffected: 5.15.210 , ≤ 5.15.* (semver)
Unaffected: 6.1.176 , ≤ 6.1.* (semver)
Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.12.93 , ≤ 6.12.* (semver)
Unaffected: 6.18.35 , ≤ 6.18.* (semver)
Unaffected: 7.0.12 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()\n\nipv6_rpl_srh_decompress() computes:\n\n    outhdr-\u003ehdrlen = (((n + 1) * sizeof(struct in6_addr)) \u003e\u003e 3);\n\nhdrlen is __u8. For n \u003e= 127 the result exceeds 255 and silently\ntruncates. With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16):\n\n    (128 * 16) \u003e\u003e 3 = 256, truncated to 0 as __u8\n\nThe caller in ipv6_rpl_srh_rcv() then places the compressed header\nat buf + ((ohdr-\u003ehdrlen + 1) \u003c\u003c 3). With hdrlen=0 this is buf + 8,\nbut the decompressed region occupies buf[0..2055] (8-byte header\nplus 128 full addresses). The compressed header overlaps the\ndecompressed data, and ipv6_rpl_srh_compress() writes into this\noverlap, corrupting the routing header of the forwarded packet.\n\nThe existing guard at exthdrs.c:546 checks (n + 1) \u003e 255, which\nprevents n+1 from overflowing unsigned char (the segments_left\nfield), but does not prevent the computed hdrlen from overflowing\n__u8. n=127 passes because 128 \u003c= 255, yet hdrlen=256 does not\nfit.\n\nTighten the bound to (n + 1) \u003e 127. This caps n at 126, giving\nhdrlen = (127 * 16) \u003e\u003e 3 = 254, which fits in __u8. The compressed\nheader then lands at buf + ((254 + 1) \u003c\u003c 3) = buf + 2040, exactly\npast the decompressed region (buf[0..2039]). No overlap. 127\nsegments is well beyond any realistic RPL deployment."
        }
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            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
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      "providerMetadata": {
        "dateUpdated": "2026-07-20T13:42:04.995Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed"
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          "url": "https://git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1"
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        {
          "url": "https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679"
        }
      ],
      "title": "ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()",
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    "dateReserved": "2026-07-19T07:54:57.025Z",
    "dateUpdated": "2026-07-20T13:42:04.995Z",
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      "date": "2026-07-21",
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With hdrlen=0 this is buf + 8,\\nbut the decompressed region occupies buf[0..2055] (8-byte header\\nplus 128 full addresses). The compressed header overlaps the\\ndecompressed data, and ipv6_rpl_srh_compress() writes into this\\noverlap, corrupting the routing header of the forwarded packet.\\n\\nThe existing guard at exthdrs.c:546 checks (n + 1) \u003e 255, which\\nprevents n+1 from overflowing unsigned char (the segments_left\\nfield), but does not prevent the computed hdrlen from overflowing\\n__u8. n=127 passes because 128 \u003c= 255, yet hdrlen=256 does not\\nfit.\\n\\nTighten the bound to (n + 1) \u003e 127. This caps n at 126, giving\\nhdrlen = (127 * 16) \u003e\u003e 3 = 254, which fits in __u8. The compressed\\nheader then lands at buf + ((254 + 1) \u003c\u003c 3) = buf + 2040, exactly\\npast the decompressed region (buf[0..2039]). No overlap. 127\\nsegments is well beyond any realistic RPL deployment.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/ipv6/exthdrs.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\"lessThan\":\"75b3680047bf09af8e7e471a7a6ddf2ce5847f56\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\"lessThan\":\"fd238c51b0fa5390cceca9f1ac5a9ffda8063eed\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\"lessThan\":\"3618b34942b76471d044369bfd30d58c39068bf1\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\"lessThan\":\"97e06791368c01f0ad2a4b3269c2abe19485ca32\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\"lessThan\":\"de02fc049352af5a9595f015511222d0a85c326b\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\"lessThan\":\"6fe1cb312038516cb4d9fa089d700af7059f1a64\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\"lessThan\":\"c0487a9c1e116cf349e2d1f302d9019670460858\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\"lessThan\":\"9d5e7a46a9f6d8f503b41bfefef70659845f1679\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/ipv6/exthdrs.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.7\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.7\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.10.259\",\"lessThanOrEqual\":\"5.10.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.210\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.1.176\",\"lessThanOrEqual\":\"6.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.143\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.93\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.35\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.0.12\",\"lessThanOrEqual\":\"7.0.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":9.8,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/6fe1cb312038516cb4d9fa089d700af7059f1a64\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/75b3680047bf09af8e7e471a7a6ddf2ce5847f56\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/97e06791368c01f0ad2a4b3269c2abe19485ca32\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c0487a9c1e116cf349e2d1f302d9019670460858\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}



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