High severity · published Oct 23, 2026
CVE-2026-99042
io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6
New
8.4
CVSS
0.2%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 5% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
LI
Linux · Linux
899bea8248cee35d54760a5e7d61a76af8e64411 before 596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5; 899bea8248cee35d54760a5e7d61a76af8e64411 before aa5d5f8e502318e783545ba5d04bb40130b83e20; 7.2 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-99042
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-99042
git.kernel.org
https://git.kernel.org/stable/c/596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5
git.kernel.org
https://git.kernel.org/stable/c/aa5d5f8e502318e783545ba5d04bb40130b83e20
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