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5.5Medium

Linux Linux Kernel

CVE-2026-45841

In the Linux kernel, the following vulnerability has been resolved: netfilter: nfnetlink_osf: fix divide-by-zero in OSF_WSS_MODULO nf_osf_match_one() computes ctx->window % f->wss.val in the OSF_WSS_MODULO branch with no guard for f->wss.val == 0. A CAP_NET_ADMIN user can add such a fingerprint via nfnetlink; a subsequent matching TCP SYN divides by zero and panics the kernel. Reject the bogus fingerprint in nfnl_osf_add_callback() above the per-option for-loop. f->wss is per-fingerprint, not per-option, so the check must run regardless of f->opt_num (including 0). Also reject wss.wc >= OSF_WSS_MAX; nf_osf_match_one() already treats that as "should not happen". Crash: Oops: divide error: 0000 [#1] SMP KASAN NOPTI RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98) Call Trace: nf_osf_match (net/netfilter/nfnetlink_osf.c:220) xt_osf_match_packet (net/netfilter/xt_osf.c:32) ipt_do_table (net/ipv4/netfilter/ip_tables.c:348) nf_hook_slow (net/netfilter/core.c:622) ip_local_deliver (net/ipv4/ip_input.c:265) ip_rcv (include/linux/skbuff.h:1162) __netif_receive_skb_one_core (net/core/dev.c:6181) process_backlog (net/core/dev.c:6642) __napi_poll (net/core/dev.c:7710) net_rx_action (net/core/dev.c:7945) handle_softirqs (kernel/softirq.c:622)

What this means for your business

  • It affects Linux Kernel. It matters if your company, or a supplier that handles your data, runs it.
  • An attacker can use it only with access to the machine itself, with an ordinary user login, and without anyone at your company clicking anything.
  • FIRST's prediction model gives it a 0.1% chance of attack attempts being seen in the next 30 days, ranking above 2% of all known flaws.

What to do

  1. 1Check whether your company or your suppliers run Linux Kernel, and which version. The affected versions are listed further down this page.
  2. 2If you do, apply the vendor's fix. A patch or vendor advisory has been published.

Not sure if your company is exposed?

Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.

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Scoring

CVSS
5.5 (v3.1)
Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-369
Assigned by
416baaa9-dc9f-4396-8d5f-8c081fb06d67

Dates

Published
2026-05-27
Last modified
2026-09-08
Sources
NVD

Affected products

  • Linux Linux Kernel2.6.31 - 5.10.258, 5.11 - 5.15.209, 5.16 - 6.1.175, 6.2 - 6.6.141, 6.7 - 6.12.91, 6.13 - 6.18.33, 6.19 - 7.0.10

As listed in the NVD configuration data. Not a statement about your estate.

References