high · 8.4

In the Linux kernel, the following vulnerability has been resolved: io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in…

CVE-2026-99042 · GHSA-cg89-27g3-43v4 · EUVD-2026-108837 · published 23 Oct 2026

How serious is it

  • Severity: high, CVSS score 8.4 out of 10.
  • No exploit prediction (EPSS) score yet.
  • Not on the CISA list of exploited vulnerabilities.
  • No public exploit in Exploit-DB.

Is your app affected by CVE-2026-99042?

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Who is affected

  • Linux Linux: 899bea8248cee35d54760a5e7d61a76af8e64411 <aa5d5f8e502318e783545ba5d04bb40130b83e20
  • Linux Linux: patch: 7.3
  • Linux Linux: 7.2
  • Linux Linux: 899bea8248cee35d54760a5e7d61a76af8e64411 <596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5
  • Linux Linux: patch: 7.2.11
  • Linux Linux: patch: 0

How to check

  1. Find out whether you run the affected product and which version, then compare it with the versions above.

How to fix

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  1. Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
  2. If a vulnerable version was live, check your logs and rotate the secrets that server could read.

The advisory

In the Linux kernel, the following vulnerability has been resolved: io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6 io_connect_bpf_populate() fills connect.port and connect.v6_addr for AF_INET6 only when addr_len >= sizeof(struct sockaddr_in6), i.e. 28 bytes. The IPv6 connect paths accept SIN6_LEN_RFC2133 (24 bytes), which already holds sin6_port and sin6_addr. io_connect() passes addr_len to the socket layer unchanged. At addr_len 24 the filter sees family AF_INET6 with port and address zero, while the kernel connects to the real destination. A filter that denies an IPv6 port or address is bypassed. Denying connect.port == P rejects [::1]:P with -EACCES at addr_len 28 but connects at addr_len 24. Use SIN6_LEN_RFC2133 as the threshold. sin6_scope_id stays zero when absent. The threshold mismatch was found by an AI coding assistant (Claude Code) comparing this hook against the net/ipv6 length checks on my instructions; it also drafted the reproducer and this patch. I verified the bypass and the fix in a VM on 7.3-rc6 and that 7.2 has the same code.

Check your whole app

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References

Merged from ENISA EUVD. Last updated 25 Oct 2026. All vulnerabilities · RSS · JSON

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