CVE-2026-43037 (GCVE-0-2026-43037)
Vulnerability from cvelistv5 – Published: 2026-05-01 14:15 – Updated: 2026-05-03 05:46
VLAI?
Title
ip6_tunnel: clear skb2->cb[] in ip4ip6_err()
Summary
In the Linux kernel, the following vulnerability has been resolved:
ip6_tunnel: clear skb2->cb[] in ip4ip6_err()
Oskar Kjos reported the following problem.
ip4ip6_err() calls icmp_send() on a cloned skb whose cb[] was written
by the IPv6 receive path as struct inet6_skb_parm. icmp_send() passes
IPCB(skb2) to __ip_options_echo(), which interprets that cb[] region
as struct inet_skb_parm (IPv4). The layouts differ: inet6_skb_parm.nhoff
at offset 14 overlaps inet_skb_parm.opt.rr, producing a non-zero rr
value. __ip_options_echo() then reads optlen from attacker-controlled
packet data at sptr[rr+1] and copies that many bytes into dopt->__data,
a fixed 40-byte stack buffer (IP_OPTIONS_DATA_FIXED_SIZE).
To fix this we clear skb2->cb[], as suggested by Oskar Kjos.
Also add minimal IPv4 header validation (version == 4, ihl >= 5).
Severity ?
9.8 (Critical)
Assigner
References
Impacted products
| Vendor | Product | Version | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux |
Affected:
c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < ea9f65b27c8404e164848ebff1443310fd187629
(git)
Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < d6621f60192fe10c047a4487be42a6f4c150707f (git) Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < 2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5 (git) Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < a0c4ce9900a108eaf55d0f3b399cb55999647d39 (git) Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < 1063515ce15ff31065c4e7f8265f4c2fd3c54876 (git) Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < 590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3 (git) Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < 4a622658f384b03560834cbe8ffcfe69a278f7c8 (git) Affected: c4d3efafcc933fd2ffd169d7dc4f980393a13796 , < 2edfa31769a4add828a7e604b21cb82aaaa05925 (git) |
|||||||
|
|||||||||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/ipv6/ip6_tunnel.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "ea9f65b27c8404e164848ebff1443310fd187629",
"status": "affected",
"version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
"versionType": "git"
},
{
"lessThan": "d6621f60192fe10c047a4487be42a6f4c150707f",
"status": "affected",
"version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
"versionType": "git"
},
{
"lessThan": "2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5",
"status": "affected",
"version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
"versionType": "git"
},
{
"lessThan": "a0c4ce9900a108eaf55d0f3b399cb55999647d39",
"status": "affected",
"version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
"versionType": "git"
},
{
"lessThan": "1063515ce15ff31065c4e7f8265f4c2fd3c54876",
"status": "affected",
"version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
"versionType": "git"
},
{
"lessThan": "590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3",
"status": "affected",
"version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
"versionType": "git"
},
{
"lessThan": "4a622658f384b03560834cbe8ffcfe69a278f7c8",
"status": "affected",
"version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
"versionType": "git"
},
{
"lessThan": "2edfa31769a4add828a7e604b21cb82aaaa05925",
"status": "affected",
"version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/ipv6/ip6_tunnel.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.22"
},
{
"lessThan": "2.6.22",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.253",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.203",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.168",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.134",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.81",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.22",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.19.*",
"status": "unaffected",
"version": "6.19.12",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.0",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.253",
"versionStartIncluding": "2.6.22",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.15.203",
"versionStartIncluding": "2.6.22",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.168",
"versionStartIncluding": "2.6.22",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.134",
"versionStartIncluding": "2.6.22",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.81",
"versionStartIncluding": "2.6.22",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.22",
"versionStartIncluding": "2.6.22",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.19.12",
"versionStartIncluding": "2.6.22",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.0",
"versionStartIncluding": "2.6.22",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nip6_tunnel: clear skb2-\u003ecb[] in ip4ip6_err()\n\nOskar Kjos reported the following problem.\n\nip4ip6_err() calls icmp_send() on a cloned skb whose cb[] was written\nby the IPv6 receive path as struct inet6_skb_parm. icmp_send() passes\nIPCB(skb2) to __ip_options_echo(), which interprets that cb[] region\nas struct inet_skb_parm (IPv4). The layouts differ: inet6_skb_parm.nhoff\nat offset 14 overlaps inet_skb_parm.opt.rr, producing a non-zero rr\nvalue. __ip_options_echo() then reads optlen from attacker-controlled\npacket data at sptr[rr+1] and copies that many bytes into dopt-\u003e__data,\na fixed 40-byte stack buffer (IP_OPTIONS_DATA_FIXED_SIZE).\n\nTo fix this we clear skb2-\u003ecb[], as suggested by Oskar Kjos.\n\nAlso add minimal IPv4 header validation (version == 4, ihl \u003e= 5)."
}
],
"metrics": [
{
"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"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-05-03T05:46:16.322Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/ea9f65b27c8404e164848ebff1443310fd187629"
},
{
"url": "https://git.kernel.org/stable/c/d6621f60192fe10c047a4487be42a6f4c150707f"
},
{
"url": "https://git.kernel.org/stable/c/2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5"
},
{
"url": "https://git.kernel.org/stable/c/a0c4ce9900a108eaf55d0f3b399cb55999647d39"
},
{
"url": "https://git.kernel.org/stable/c/1063515ce15ff31065c4e7f8265f4c2fd3c54876"
},
{
"url": "https://git.kernel.org/stable/c/590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3"
},
{
"url": "https://git.kernel.org/stable/c/4a622658f384b03560834cbe8ffcfe69a278f7c8"
},
{
"url": "https://git.kernel.org/stable/c/2edfa31769a4add828a7e604b21cb82aaaa05925"
}
],
"title": "ip6_tunnel: clear skb2-\u003ecb[] in ip4ip6_err()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-43037",
"datePublished": "2026-05-01T14:15:35.314Z",
"dateReserved": "2026-05-01T14:12:55.978Z",
"dateUpdated": "2026-05-03T05:46:16.322Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-43037",
"date": "2026-05-04",
"epss": "0.00053",
"percentile": "0.16425"
},
"nvd": "{\"cve\":{\"id\":\"CVE-2026-43037\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-05-01T15:16:48.383\",\"lastModified\":\"2026-05-04T18:26:53.743\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nip6_tunnel: clear skb2-\u003ecb[] in ip4ip6_err()\\n\\nOskar Kjos reported the following problem.\\n\\nip4ip6_err() calls icmp_send() on a cloned skb whose cb[] was written\\nby the IPv6 receive path as struct inet6_skb_parm. icmp_send() passes\\nIPCB(skb2) to __ip_options_echo(), which interprets that cb[] region\\nas struct inet_skb_parm (IPv4). The layouts differ: inet6_skb_parm.nhoff\\nat offset 14 overlaps inet_skb_parm.opt.rr, producing a non-zero rr\\nvalue. __ip_options_echo() then reads optlen from attacker-controlled\\npacket data at sptr[rr+1] and copies that many bytes into dopt-\u003e__data,\\na fixed 40-byte stack buffer (IP_OPTIONS_DATA_FIXED_SIZE).\\n\\nTo fix this we clear skb2-\u003ecb[], as suggested by Oskar Kjos.\\n\\nAlso add minimal IPv4 header validation (version == 4, ihl \u003e= 5).\"}],\"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}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-787\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"2.6.22\",\"versionEndExcluding\":\"5.10.253\",\"matchCriteriaId\":\"2FAF7ECB-85CC-455A-BD37-B1C507BDF01A\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.11\",\"versionEndExcluding\":\"5.15.203\",\"matchCriteriaId\":\"20DDB3E9-AABF-4107-ADB0-5362AA067045\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"5.16\",\"versionEndExcluding\":\"6.1.168\",\"matchCriteriaId\":\"E2DDDCA1-6DAB-4018-B920-8F045DDD8D3B\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.2\",\"versionEndExcluding\":\"6.6.134\",\"matchCriteriaId\":\"F56F925B-BAF8-4F4B-B62F-1496AF19A307\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.7\",\"versionEndExcluding\":\"6.12.81\",\"matchCriteriaId\":\"6EF80433-B33B-43C5-8E64-0FA7B8DCE1BC\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.13\",\"versionEndExcluding\":\"6.18.22\",\"matchCriteriaId\":\"C9DF8BCE-36D3-475D-9D21-19E4F02F9029\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.19\",\"versionEndExcluding\":\"6.19.12\",\"matchCriteriaId\":\"0A2B9540-02D5-41B4-B16A-82AF66FD4F36\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*\",\"matchCriteriaId\":\"F253B622-8837-4245-BCE5-A7BF8FC76A16\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*\",\"matchCriteriaId\":\"4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*\",\"matchCriteriaId\":\"F666C8D8-6538-46D4-B318-87610DE64C34\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*\",\"matchCriteriaId\":\"02259FDA-961B-47BC-AE7F-93D7EC6E90C2\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*\",\"matchCriteriaId\":\"58A9FEFF-C040-420D-8F0A-BFDAAA1DF258\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*\",\"matchCriteriaId\":\"1D2315C0-D46F-4F85-9754-F9E5E11374A6\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/1063515ce15ff31065c4e7f8265f4c2fd3c54876\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/2edfa31769a4add828a7e604b21cb82aaaa05925\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/4a622658f384b03560834cbe8ffcfe69a278f7c8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/a0c4ce9900a108eaf55d0f3b399cb55999647d39\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/d6621f60192fe10c047a4487be42a6f4c150707f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/ea9f65b27c8404e164848ebff1443310fd187629\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]}]}}"
}
}
Loading…
Loading…
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.
Loading…
Loading…