CVE-2026-52999 netfilter: nfnetlink_osf: fix out-of-bounds read on option matching
An out-of-bounds read in the Linux kernel netfilter OSF module allows attackers to read garbage data when logging is enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-52999?
CVE-2026-52999 is a critical vulnerability in Linux kernel, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nfnetlink_osf: fix out-of-bounds read on option matching
In nf_osf_match(), the nf_osf_hdr_ctx structure is initialized once and passed by reference to nf_osf_match_one() for each fingerprint checked. During TCP option parsing, nf_osf_match_one() advances the shared ctx->optp pointer.
If a fingerprint perfectly matches, the function returns early without restoring ctx->optp to its initial state. If the user has configured NF_OSF_LOGLEVEL_ALL, the loop continues to the next fingerprint. However, because ctx->optp was not restored, the next call to nf_osf_match_one() starts parsing from the end of the options buffer. This causes subsequent matches to read garbage data and fail immediately, making it impossible to log more than one match or logging incorrect matches.
Instead of using a shared ctx->optp pointer, pass the context as a constant pointer and use a local pointer (optp) for TCP option traversal. This makes nf_osf_match_one() strictly stateless from the caller's perspective, ensuring every fingerprint check starts at the correct option offset.
Weakness: CWE-125
Which versions are affected by CVE-2026-52999?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-52999?
Apply the vendor's patch.
Is CVE-2026-52999 being exploited?
There is no known exploitation of CVE-2026-52999 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-52999, DEBIAN-CVE-2026-52999, GHSA-vhgw-q6q5-v9w3, ROOT-OS-DEBIAN-11-CVE-2026-52999, ROOT-OS-DEBIAN-12-CVE-2026-52999, ROOT-OS-UBUNTU-2204-CVE-2026-52999 and 2 more.