CVE-2026-43038 (GCVE-0-2026-43038)
Vulnerability from cvelistv5 – Published: 2026-05-01 14:15 – Updated: 2026-05-03 05:46
VLAI?
Title
ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()
Summary
In the Linux kernel, the following vulnerability has been resolved:
ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()
Sashiko AI-review observed:
In ip6_err_gen_icmpv6_unreach(), the skb is an outer IPv4 ICMP error packet
where its cb contains an IPv4 inet_skb_parm. When skb is cloned into skb2
and passed to icmp6_send(), it uses IP6CB(skb2).
IP6CB interprets the IPv4 inet_skb_parm as an inet6_skb_parm. The cipso
offset in inet_skb_parm.opt directly overlaps with dsthao in inet6_skb_parm
at offset 18.
If an attacker sends a forged ICMPv4 error with a CIPSO IP option, dsthao
would be a non-zero offset. Inside icmp6_send(), mip6_addr_swap() is called
and uses ipv6_find_tlv(skb, opt->dsthao, IPV6_TLV_HAO).
This would scan the inner, attacker-controlled IPv6 packet starting at that
offset, potentially returning a fake TLV without checking if the remaining
packet length can hold the full 18-byte struct ipv6_destopt_hao.
Could mip6_addr_swap() then perform a 16-byte swap that extends past the end
of the packet data into skb_shared_info?
Should the cb array also be cleared in ip6_err_gen_icmpv6_unreach() and
ip6ip6_err() to prevent this?
This patch implements the first suggestion.
I am not sure if ip6ip6_err() needs to be changed.
A separate patch would be better anyway.
Severity ?
9.8 (Critical)
Assigner
References
Impacted products
| Vendor | Product | Version | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux |
Affected:
ca15a078bd907df5fc1c009477869c5cbde3b753 , < c438ba010171b70bad22fc18b1d5bdc3627476e8
(git)
Affected: ca15a078bd907df5fc1c009477869c5cbde3b753 , < 0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7 (git) Affected: ca15a078bd907df5fc1c009477869c5cbde3b753 , < a4437faf135da293d16fcc4cc607316742bd0ebb (git) Affected: ca15a078bd907df5fc1c009477869c5cbde3b753 , < 3d5127d998de617b130aae96b138dba22ac6a8a7 (git) Affected: ca15a078bd907df5fc1c009477869c5cbde3b753 , < e41953e7d118e2702bcb217879c173d9d1d3cd4e (git) Affected: ca15a078bd907df5fc1c009477869c5cbde3b753 , < a2edbb6393972a02114b6003953a5cef3104fada (git) Affected: ca15a078bd907df5fc1c009477869c5cbde3b753 , < 1ceeebd5bd6d855b17a5df625109bfe29129d7cf (git) Affected: ca15a078bd907df5fc1c009477869c5cbde3b753 , < 86ab3e55673a7a49a841838776f1ab18d23a67b5 (git) |
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|
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{
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"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.*",
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{
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{
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{
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{
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: icmp: clear skb2-\u003ecb[] in ip6_err_gen_icmpv6_unreach()\n\nSashiko AI-review observed:\n\n In ip6_err_gen_icmpv6_unreach(), the skb is an outer IPv4 ICMP error packet\n where its cb contains an IPv4 inet_skb_parm. When skb is cloned into skb2\n and passed to icmp6_send(), it uses IP6CB(skb2).\n\n IP6CB interprets the IPv4 inet_skb_parm as an inet6_skb_parm. The cipso\n offset in inet_skb_parm.opt directly overlaps with dsthao in inet6_skb_parm\n at offset 18.\n\n If an attacker sends a forged ICMPv4 error with a CIPSO IP option, dsthao\n would be a non-zero offset. Inside icmp6_send(), mip6_addr_swap() is called\n and uses ipv6_find_tlv(skb, opt-\u003edsthao, IPV6_TLV_HAO).\n\n This would scan the inner, attacker-controlled IPv6 packet starting at that\n offset, potentially returning a fake TLV without checking if the remaining\n packet length can hold the full 18-byte struct ipv6_destopt_hao.\n\n Could mip6_addr_swap() then perform a 16-byte swap that extends past the end\n of the packet data into skb_shared_info?\n\n Should the cb array also be cleared in ip6_err_gen_icmpv6_unreach() and\n ip6ip6_err() to prevent this?\n\nThis patch implements the first suggestion.\n\nI am not sure if ip6ip6_err() needs to be changed.\nA separate patch would be better anyway."
}
],
"metrics": [
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"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": "2026-05-03T05:46:17.465Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
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"url": "https://git.kernel.org/stable/c/c438ba010171b70bad22fc18b1d5bdc3627476e8"
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{
"url": "https://git.kernel.org/stable/c/0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7"
},
{
"url": "https://git.kernel.org/stable/c/a4437faf135da293d16fcc4cc607316742bd0ebb"
},
{
"url": "https://git.kernel.org/stable/c/3d5127d998de617b130aae96b138dba22ac6a8a7"
},
{
"url": "https://git.kernel.org/stable/c/e41953e7d118e2702bcb217879c173d9d1d3cd4e"
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{
"url": "https://git.kernel.org/stable/c/a2edbb6393972a02114b6003953a5cef3104fada"
},
{
"url": "https://git.kernel.org/stable/c/1ceeebd5bd6d855b17a5df625109bfe29129d7cf"
},
{
"url": "https://git.kernel.org/stable/c/86ab3e55673a7a49a841838776f1ab18d23a67b5"
}
],
"title": "ipv6: icmp: clear skb2-\u003ecb[] in ip6_err_gen_icmpv6_unreach()",
"x_generator": {
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"assignerShortName": "Linux",
"cveId": "CVE-2026-43038",
"datePublished": "2026-05-01T14:15:35.986Z",
"dateReserved": "2026-05-01T14:12:55.978Z",
"dateUpdated": "2026-05-03T05:46:17.465Z",
"state": "PUBLISHED"
},
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"cve": "CVE-2026-43038",
"date": "2026-05-05",
"epss": "0.00053",
"percentile": "0.16406"
},
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}
}
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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.
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