CVE-2026-43037 (GCVE-0-2026-43037)
Vulnerability from cvelistv5
Published
2026-05-01 14:15
Modified
2026-05-03 05:46
Severity ?
VLAI Severity ?
EPSS score ?
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).
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: c4d3efafcc933fd2ffd169d7dc4f980393a13796 Version: c4d3efafcc933fd2ffd169d7dc4f980393a13796 Version: c4d3efafcc933fd2ffd169d7dc4f980393a13796 Version: c4d3efafcc933fd2ffd169d7dc4f980393a13796 Version: c4d3efafcc933fd2ffd169d7dc4f980393a13796 Version: c4d3efafcc933fd2ffd169d7dc4f980393a13796 Version: c4d3efafcc933fd2ffd169d7dc4f980393a13796 Version: c4d3efafcc933fd2ffd169d7dc4f980393a13796 |
||
{
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{
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],
"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": {
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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"
}
}
],
"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"
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{
"url": "https://git.kernel.org/stable/c/590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3"
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{
"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": {
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}
},
"cveMetadata": {
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"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"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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