CVE-2026-99042
io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6
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.
INFO
Published Date :
Oct. 23, 2026, 1:17 p.m.
Last Modified :
Oct. 23, 2026, 1:17 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Apply the kernel patch addressing the sockaddr_in6 length mismatch.
- Update the Linux kernel to a fixed version.
- Verify the BPF filter logic post-update.
- Ensure correct connection filtering.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-99042.
| URL | Resource |
|---|---|
| https://git.kernel.org/stable/c/596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5 | |
| https://git.kernel.org/stable/c/aa5d5f8e502318e783545ba5d04bb40130b83e20 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-99042 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-99042
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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The following list is the news that have been mention
CVE-2026-99042 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-99042 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Oct. 23, 2026
Action Type Old Value New Value Added 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. Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/99xxx/CVE-2026-99042.json">CVE-2026-99042</a> Added Reference https://git.kernel.org/stable/c/596a955d2d01b7e29d9fed60ebcf7c4ba518b8e5 Added Reference https://git.kernel.org/stable/c/aa5d5f8e502318e783545ba5d04bb40130b83e20