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CVE-2026-68118

HIGHCVSS 8.2/10EPSS 0.38%

Last modified

CVE-2026-68118 is a high-severity vulnerability rated 8.2/10 on the CVSS scale. 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. EPSS estimates a 0.38% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1
8.2/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

EPSS Probability
0.38%

31.8th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 282f23c6ee343126156dd41218b22ece96d747e3, < 8b0a3a094f4cae2fb92e4d08d4eef7246a9d9c49; >= 282f23c6ee343126156dd41218b22ece96d747e3, < 0fe4636665d14a258de70b4f3e8248e6d42038f1; >= 282f23c6ee343126156dd41218b22ece96d747e3, < 234f9ffbd9b2c1b24ec67200ea3cff07401bec48; >= 282f23c6ee343126156dd41218b22ece96d747e3, < 22cec809b048495310f206d9abbcdbbfbdce3ae3; >= 282f23c6ee343126156dd41218b22ece96d747e3, < a28c4fcbf774e23b4779cae468e3497a5ad1f4a1; 86791bbfe5ed7b275be040cfeff049a1624af1b7; 61f69dc4e40e41b0018f00fa4aeb23d3239556fb; 34fb350281ced2a72707a5c0064f69992d440edb; >= 3.0.58, < 3.1; >= 3.2.37, < 3.3; >= 3.4.25, < 3.5
LinuxLinux3.6

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is CVE-2026-68118?
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.
How severe is CVE-2026-68118?
CVE-2026-68118 has a CVSS score of 8.2/10 (HIGH severity). The EPSS model estimates a 0.38% probability of exploitation in the next 30 days.
How do I fix CVE-2026-68118?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST