CVE-2026-63984 (GCVE-0-2026-63984)
Vulnerability from cvelistv5 – Published: 2026-07-19 14:56 – Updated: 2026-10-19 20:18
VLAI
EPSS
VEX
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)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 15:34 UTC
CWE
- CWE-190 - Integer Overflow or Wraparound
Assigner
References
8 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| 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) |
guessed | |
| 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) |
guessed |
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"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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"value": "AV:N - The vulnerable code runs in the IPv6 routing-header receive handler on incoming packets; a remote attacker can deliver a crafted RFC 6554 type-3 RPL SRH to an RPL-enabled router or gateway over the network.\nAC:L - Triggering requires only a deterministically crafted SRH (e.g., n=127, CmprI=15, CmprE=15, pad=0, hdrlen=16, segments_left\u003e0); all of these fields are fully attacker-controlled once the target has rpl_seg_enabled.\nPR:N - No authentication or local privileges are needed to send the malicious IPv6 packet; rpl_seg_enabled is a victim-side deployment setting on RPL routers/gateways (IoT/industrial mesh), not an attacker privilege requirement.\nUI:N - Exploitation is achieved solely by sending a malformed network packet and does not require any action from a victim user.\nS:U - Impact is confined to kernel memory corruption and packet forwarding within the same kernel security boundary; this is not a VM escape, sandbox escape, or cross-authority boundary violation.\nC:H - The hdrlen truncation causes overlapping read/write of the same kmalloc buffer during decompress/recompress, constituting kernel heap memory corruption that can be leveraged for information disclosure primitives.\nI:H - ipv6_rpl_srh_compress() performs out-of-bounds writes into the overlapping decompressed region, corrupting routing-header data that is then memcpy\u0027d into the forwarded skb, enabling memory corruption exploitable for control-flow or data modification.\nA:H - Kernel heap corruption during SRH processing can cause kernel oops, panics, or repeated crashes when processing or forwarding the corrupted packet, consistent with high availability impact for memory-corruption bugs."
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"title": "ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()",
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"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."
}
],
"id": "CVE-2026-63984",
"lastModified": "2026-10-19T21:17:16.390",
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"attackVector": "NETWORK",
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"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
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"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
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"type": "Secondary"
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},
"published": "2026-07-19T16:17:17.590",
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},
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},
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{
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"url": "https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b"
},
{
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"url": "https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Undergoing Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-190"
}
],
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary"
}
]
}
},
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-10-16T17:34:29+00:00",
"cve": "CVE-2026-63984",
"id": "CVE-2026-63984",
"initial_release_date": "2026-07-19T00:00:00+00:00",
"product_status:fixed": "1148",
"product_status:known_affected": "113",
"product_status:known_not_affected": "76",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63984.json",
"version": "3"
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-63984",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-16T15:34:39.184194Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-190",
"description": "CWE-190 Integer Overflow or Wraparound",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-16T15:34:39.740Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/ipv6/exthdrs.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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"version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3",
"versionType": "git"
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{
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"status": "affected",
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{
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{
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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"version": "5.7"
},
{
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"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
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"status": "unaffected",
"version": "5.10.259",
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{
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"status": "unaffected",
"version": "5.15.210",
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{
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{
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"version": "6.6.143",
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{
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"version": "6.12.93",
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},
{
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"status": "unaffected",
"version": "6.18.35",
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},
{
"lessThanOrEqual": "7.0.*",
"status": "unaffected",
"version": "7.0.12",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.1",
"versionType": "original_commit_for_fix"
}
]
}
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"vulnerable": true
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"descriptions": [
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"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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"cvssV3_1": {
"baseScore": 9.8,
"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"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - The vulnerable code runs in the IPv6 routing-header receive handler on incoming packets; a remote attacker can deliver a crafted RFC 6554 type-3 RPL SRH to an RPL-enabled router or gateway over the network.\nAC:L - Triggering requires only a deterministically crafted SRH (e.g., n=127, CmprI=15, CmprE=15, pad=0, hdrlen=16, segments_left\u003e0); all of these fields are fully attacker-controlled once the target has rpl_seg_enabled.\nPR:N - No authentication or local privileges are needed to send the malicious IPv6 packet; rpl_seg_enabled is a victim-side deployment setting on RPL routers/gateways (IoT/industrial mesh), not an attacker privilege requirement.\nUI:N - Exploitation is achieved solely by sending a malformed network packet and does not require any action from a victim user.\nS:U - Impact is confined to kernel memory corruption and packet forwarding within the same kernel security boundary; this is not a VM escape, sandbox escape, or cross-authority boundary violation.\nC:H - The hdrlen truncation causes overlapping read/write of the same kmalloc buffer during decompress/recompress, constituting kernel heap memory corruption that can be leveraged for information disclosure primitives.\nI:H - ipv6_rpl_srh_compress() performs out-of-bounds writes into the overlapping decompressed region, corrupting routing-header data that is then memcpy\u0027d into the forwarded skb, enabling memory corruption exploitable for control-flow or data modification.\nA:H - Kernel heap corruption during SRH processing can cause kernel oops, panics, or repeated crashes when processing or forwarding the corrupted packet, consistent with high availability impact for memory-corruption bugs."
}
]
}
],
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"dateUpdated": "2026-08-05T12:37:52.442Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
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},
{
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},
{
"url": "https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b"
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},
{
"url": "https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679"
}
],
"title": "ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()",
"x_generator": {
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},
"cveMetadata": {
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"assignerShortName": "Linux",
"cveId": "CVE-2026-63984",
"datePublished": "2026-07-19T14:56:06.786Z",
"dateReserved": "2026-07-19T07:54:57.025Z",
"dateUpdated": "2026-10-19T20:18:00.765Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
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}
}
}
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.