FKIE_CVE-2026-43038
Vulnerability from fkie_nvd - Published: 2026-05-01 15:16 - Updated: 2026-05-03 07:16
Severity ?
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.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"cveTags": [],
"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."
}
],
"id": "CVE-2026-43038",
"lastModified": "2026-05-03T07:16:23.417",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
]
},
"published": "2026-05-01T15:16:48.533",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/1ceeebd5bd6d855b17a5df625109bfe29129d7cf"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/3d5127d998de617b130aae96b138dba22ac6a8a7"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/86ab3e55673a7a49a841838776f1ab18d23a67b5"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/a2edbb6393972a02114b6003953a5cef3104fada"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/a4437faf135da293d16fcc4cc607316742bd0ebb"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/c438ba010171b70bad22fc18b1d5bdc3627476e8"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/e41953e7d118e2702bcb217879c173d9d1d3cd4e"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Awaiting Analysis"
}
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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.
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- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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