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tcp: challenge ACK for non-exact RST in SYN-RECEIVED
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.
References
Affected products
- ==34fb350281ced2a72707a5c0064f69992d440edb
- <3.3
- ==3.6
- ==61f69dc4e40e41b0018f00fa4aeb23d3239556fb
- <234f9ffbd9b2c1b24ec67200ea3cff07401bec48
- =<*
- =<6.18.*
- <3.6
- <3.5
- <3.1
- =<7.1.*
- <22cec809b048495310f206d9abbcdbbfbdce3ae3
- ==86791bbfe5ed7b275be040cfeff049a1624af1b7
- <a28c4fcbf774e23b4779cae468e3497a5ad1f4a1