Description
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.
Published: 2026-05-01
Score: 9.8 Critical
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Analysis and contextual insights are available on OpenCVE Cloud.

Remediation

No vendor fix or workaround currently provided.

Additional remediation guidance may be available on OpenCVE Cloud.

Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-4561-1 linux-6.1 security update
Debian DLA Debian DLA DLA-4606-1 linux security update
Debian DSA Debian DSA DSA-6243-1 linux security update
Ubuntu USN Ubuntu USN USN-8490-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8491-1 Linux kernel (OEM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8492-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8493-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8492-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8493-2 Linux kernel (Oracle) vulnerabilities
Ubuntu USN Ubuntu USN USN-8497-1 Linux kernel (Low Latency) vulnerabilities
Ubuntu USN Ubuntu USN USN-8498-1 Linux kernel (NVIDIA Tegra) vulnerabilities
Ubuntu USN Ubuntu USN USN-8499-1 Linux kernel (Xilinx) vulnerabilities
Ubuntu USN Ubuntu USN USN-8501-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8508-1 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-8492-3 Linux kernel (Raspberry Pi Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-8490-2 Linux kernel (Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-8492-4 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-8492-5 Linux kernel (FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8527-1 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-8528-1 Linux kernel (Xilinx ZynqMP) vulnerabilities
Ubuntu USN Ubuntu USN USN-8529-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8530-1 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8545-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-8546-1 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-8547-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8548-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8604-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8605-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8606-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8607-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8609-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8547-2 Linux kernel (Azure FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8615-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8616-1 Linux kernel (IBM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8617-1 Linux kernel (KVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8619-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-8615-2 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-8635-1 Linux kernel (Azure) vulnerabilities
References
Link Providers
https://access.redhat.com/errata/RHSA-2026:22900 cve-icon
https://access.redhat.com/errata/RHSA-2026:22940 cve-icon
https://access.redhat.com/errata/RHSA-2026:22964 cve-icon
https://access.redhat.com/errata/RHSA-2026:23224 cve-icon
https://access.redhat.com/errata/RHSA-2026:23237 cve-icon
https://access.redhat.com/errata/RHSA-2026:24343 cve-icon
https://access.redhat.com/errata/RHSA-2026:25120 cve-icon
https://access.redhat.com/errata/RHSA-2026:25121 cve-icon
https://access.redhat.com/errata/RHSA-2026:25533 cve-icon
https://access.redhat.com/errata/RHSA-2026:26535 cve-icon
https://access.redhat.com/errata/RHSA-2026:30129 cve-icon
https://access.redhat.com/errata/RHSA-2026:30848 cve-icon
https://access.redhat.com/security/cve/CVE-2026-43038 cve-icon
https://bugzilla.redhat.com/show_bug.cgi?id=2464397 cve-icon
https://cert-portal.siemens.com/productcert/html/ssa-019113.html cve-icon
https://cert-portal.siemens.com/productcert/html/ssa-082556.html cve-icon
https://git.kernel.org/stable/c/0452b6526b2f54b2413b9cb4ff1ea2ac542c99c7 cve-icon cve-icon
https://git.kernel.org/stable/c/1ceeebd5bd6d855b17a5df625109bfe29129d7cf cve-icon cve-icon
https://git.kernel.org/stable/c/3d5127d998de617b130aae96b138dba22ac6a8a7 cve-icon cve-icon
https://git.kernel.org/stable/c/86ab3e55673a7a49a841838776f1ab18d23a67b5 cve-icon cve-icon
https://git.kernel.org/stable/c/a2edbb6393972a02114b6003953a5cef3104fada cve-icon cve-icon
https://git.kernel.org/stable/c/a4437faf135da293d16fcc4cc607316742bd0ebb cve-icon cve-icon
https://git.kernel.org/stable/c/c438ba010171b70bad22fc18b1d5bdc3627476e8 cve-icon cve-icon
https://git.kernel.org/stable/c/e41953e7d118e2702bcb217879c173d9d1d3cd4e cve-icon cve-icon
https://lore.kernel.org/linux-cve-announce/2026050103-CVE-2026-43038-b591@gregkh/T cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-43038 cve-icon
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43038.json cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-43038 cve-icon
History

Fri, 08 May 2026 19:00:00 +0000

Type Values Removed Values Added
Weaknesses NVD-CWE-noinfo
CPEs cpe:2.3:o:linux:linux_kernel:3.13:-:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:3.13:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:3.13:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:3.13:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:3.13:rc6:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:3.13:rc7:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:3.13:rc8:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*

Sun, 03 May 2026 06:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}


Sat, 02 May 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-843
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Important


Fri, 01 May 2026 14:45:00 +0000

Type Values Removed Values Added
Description 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.
Title ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-08-05T12:25:28.341Z

Reserved: 2026-05-01T14:12:55.978Z

Link: CVE-2026-43038

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Modified

Published: 2026-05-01T15:16:48.533

Modified: 2026-07-15T02:21:41.223

Link: CVE-2026-43038

cve-icon Redhat

Severity : Important

Publid Date: 2026-05-01T00:00:00Z

Links: CVE-2026-43038 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-05-08T21:00:10Z

Weaknesses