CVE-2026-43037

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Source
https://cve.org/CVERecord?id=CVE-2026-43037
Import Source
https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-43037.json
JSON Data
https://api.test.osv.dev/v1/vulns/CVE-2026-43037
Downstream
Related
Published
2026-05-01T14:15:35.314Z
Modified
2026-06-19T08:29:26.430958439Z
Severity
  • 9.8 (Critical) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H CVSS Calculator
Summary
ip6_tunnel: clear skb2->cb[] in ip4ip6_err()
Details

In the Linux kernel, the following vulnerability has been resolved:

ip6tunnel: clear skb2->cb[] in ip4ip6err()

Oskar Kjos reported the following problem.

ip4ip6err() calls icmpsend() on a cloned skb whose cb[] was written by the IPv6 receive path as struct inet6skbparm. icmp_send() passes IPCB(skb2) to __ipoptionsecho(), which interprets that cb[] region as struct inetskbparm (IPv4). The layouts differ: inet6skbparm.nhoff at offset 14 overlaps inetskbparm.opt.rr, producing a non-zero rr value. __ipoptionsecho() 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 (IPOPTIONSDATAFIXEDSIZE).

To fix this we clear skb2->cb[], as suggested by Oskar Kjos.

Also add minimal IPv4 header validation (version == 4, ihl >= 5).

Database specific 
{
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43037.json"
}
References

Affected packages

Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

Affected ranges

Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
c4d3efafcc933fd2ffd169d7dc4f980393a13796
Fixed
ea9f65b27c8404e164848ebff1443310fd187629
Fixed
d6621f60192fe10c047a4487be42a6f4c150707f
Fixed
2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5
Fixed
a0c4ce9900a108eaf55d0f3b399cb55999647d39
Fixed
1063515ce15ff31065c4e7f8265f4c2fd3c54876
Fixed
590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3
Fixed
4a622658f384b03560834cbe8ffcfe69a278f7c8
Fixed
2edfa31769a4add828a7e604b21cb82aaaa05925

Database specific

source 
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-43037.json"

Linux / Kernel

Package

Name
Kernel

Affected ranges

Type
ECOSYSTEM
Events
Introduced
2.6.22
Fixed
5.10.253
Type
ECOSYSTEM
Events
Introduced
5.11.0
Fixed
5.15.203
Type
ECOSYSTEM
Events
Introduced
5.16.0
Fixed
6.1.168
Type
ECOSYSTEM
Events
Introduced
6.2.0
Fixed
6.6.134
Type
ECOSYSTEM
Events
Introduced
6.7.0
Fixed
6.12.81
Type
ECOSYSTEM
Events
Introduced
6.13.0
Fixed
6.18.22
Type
ECOSYSTEM
Events
Introduced
6.19.0
Fixed
6.19.12

Database specific

source 
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-43037.json"