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.
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.
Published:
2026-10-23
Score:
n/a
EPSS:
n/a
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
|||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
No data available yet.
Remediation
No remediation available yet.
Tracking
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Advisories
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References
History
Fri, 23 Oct 2026 12:45:00 +0000
| Type | Values Removed | Values 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. | |
| Title | io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6 | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-10-23T12:22:01.804Z
Reserved: 2026-09-25T10:25:14.387Z
Link: CVE-2026-99042
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-23T13:17:27.610
Modified: 2026-10-23T13:17:27.610
Link: CVE-2026-99042
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.