CVE-2025-68291: In the Linux kernel, the following vulnerability has been resolved: mptcp: Initialise rcv_mss before calling tcp_send_active_reset() in mptcp_do

In the Linux kernel, the following vulnerability has been resolved: mptcp: Initialise rcv_mss before calling tcp_send_active_reset() in mptcp_do_fastclose().

In the Linux kernel, the following vulnerability has been resolved: mptcp: Initialise rcv_mss before calling tcp_send_active_reset() in mptcp_do_fastclose(). syzbot reported divide-by-zero in __tcp_select_window() by MPTCP socket. [0] We had a similar issue for the bare TCP and fixed in commit 499350a5a6e7 ("tcp: initialize rcv_mss to TCP_MIN_MSS instead of 0"). Let's apply the same fix to mptcp_do_fastclose(). [0]: Oops: divide error: 0000 [#1] SMP KASAN PTI CPU: 0 UID: 0 PID: 6068 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:__tcp_select_window+0x824/0x1320 net/ipv4/tcp_output.c:3336 Code: ff ff ff 44 89 f1 d3 e0 89 c1 f7 d1 41 01 cc 41 21 c4 e9 a9 00 00 00 e8 ca 49 01 f8 e9 9c 00 00 00 e8 c0 49 01 f8 44 89 e0 99 <f7> 7c 24 1c 41 29 d4 48 bb 00 00 00 00 00 fc ff df e9 80 00 00 00 RSP: 0018:ffffc90003017640 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88807b469e40 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffc90003017730 R08: ffff888033268143 R09: 1ffff1100664d028 R10: dffffc0000000000 R11: ffffed100664d029 R12: 00

Description from the National Vulnerability Database, published by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

What it means for a small business

Linux is on the computers, phones or browsers your team uses every day. Turn on automatic updates and restart: most of these fixes only take effect after a restart.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 0.22%, higher than 12% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 28, 2026, updated daily.

Check your own setup

Website check: reads what your site runs from the outside (WordPress version, plugins it can see, old server software) and matches it against this database.
Server check: what your web server says about itself, and whether that version has known flaws.

Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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