CVE-2026-68118

Summary

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

tcp: challenge ACK for non-exact RST in SYN-RECEIVED

The SYN-RECEIVED request-socket path in tcp_check_req() accepts an in-window RST without requiring SEG.SEQ to exactly match RCV.NXT. A non-exact RST therefore removes the request instead of eliciting a challenge ACK.

RFC 9293 section 3.10.7.4 applies the RFC 5961 reset check in SYN-RECEIVED: an exact RST resets the connection, while a non-exact in-window RST must trigger a challenge ACK and be dropped.

Apply that check before the ACK-field validation, following the RFC sequence-number, RST, then ACK processing order. Factor the per-netns challenge ACK quota out of tcp_send_challenge_ack() so request sockets can share it. Use the request socket's send_ack() callback and its own out-of-window ACK timestamp to send and rate-limit the response.

Affected Software

VendorProductVersion RangeStatus
LinuxLinux282f23c6ee343126156dd41218b22ece96d747e3 < 234f9ffbd9b2c1b24ec67200ea3cff07401bec48affected
LinuxLinux282f23c6ee343126156dd41218b22ece96d747e3 < 22cec809b048495310f206d9abbcdbbfbdce3ae3affected
LinuxLinux282f23c6ee343126156dd41218b22ece96d747e3 < a28c4fcbf774e23b4779cae468e3497a5ad1f4a1affected
LinuxLinux86791bbfe5ed7b275be040cfeff049a1624af1b7affected
LinuxLinux61f69dc4e40e41b0018f00fa4aeb23d3239556fbaffected
LinuxLinux34fb350281ced2a72707a5c0064f69992d440edbaffected
LinuxLinux3.0.58 < 3.1affected
LinuxLinux3.2.37 < 3.3affected
LinuxLinux3.4.25 < 3.5affected
LinuxLinux3.6affected
LinuxLinux0 < 3.6unaffected
LinuxLinux6.18.42 <= 6.18.*unaffected
LinuxLinux7.1.6 <= 7.1.*unaffected
LinuxLinux7.2-rc5 <= *unaffected

Weaknesses

References