CVE-2025-71160 netfilter: nf_tables: avoid chain re-validation if possible

What is CVE-2025-71160?

CVE-2025-71160 is a medium-severity denial of service vulnerability in Linux kernel, published on 23 Jan 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_tables: avoid chain re-validation if possible

Hamza Mahfooz reports cpu soft lock-ups in nft_chain_validate():

watchdog: BUG: soft lockup - CPU#1 stuck for 27s! [iptables-nft-re:37547] [..] RIP: 0010:nft_chain_validate+0xcb/0x110 [nf_tables] [..] nft_immediate_validate+0x36/0x50 [nf_tables] nft_chain_validate+0xc9/0x110 [nf_tables] nft_immediate_validate+0x36/0x50 [nf_tables] nft_chain_validate+0xc9/0x110 [nf_tables] nft_immediate_validate+0x36/0x50 [nf_tables] nft_chain_validate+0xc9/0x110 [nf_tables] nft_immediate_validate+0x36/0x50 [nf_tables] nft_chain_validate+0xc9/0x110 [nf_tables] nft_immediate_validate+0x36/0x50 [nf_tables] nft_chain_validate+0xc9/0x110 [nf_tables] nft_immediate_validate+0x36/0x50 [nf_tables] nft_chain_validate+0xc9/0x110 [nf_tables] nft_table_validate+0x6b/0xb0 [nf_tables] nf_tables_validate+0x8b/0xa0 [nf_tables] nf_tables_commit+0x1df/0x1eb0 [nf_tables] [..]

Currently nf_tables will traverse the entire table (chain graph), starting from the entry points (base chains), exploring all possible paths (chain jumps). But there are cases where we could avoid revalidation.

Consider: 1 input -> j2 -> j3 2 input -> j2 -> j3 3 input -> j1 -> j2 -> j3

Then the second rule does not need to revalidate j2, and, by extension j3, because this was already checked during validation of the first rule. We need to validate it only for rule 3.

This is needed because chain loop detection also ensures we do not exceed the jump stack: Just because we know that j2 is cycle free, its last jump might now exceed the allowed stack size. We also need to update all reachable chains with the new largest observed call depth.

Care has to be taken to revalidate even if the chain depth won't be an issue: chain validation also ensures that expressions are not called from invalid base chains. For example, the masquerade expression can only be called from NAT postrouting base chains.

Therefore we also need to keep record of the base chain context (type, hooknum) and revalidate if the chain becomes reachable from a different hook location.

Which versions are affected by CVE-2025-71160?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-71160?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2025-71160 being exploited?

There is no known exploitation of CVE-2025-71160 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-75126, AZL-78434, BELL-CVE-2025-71160, DEBIAN-CVE-2025-71160, GHSA-3xmc-22wh-x2gr, ROOT-OS-DEBIAN-11-CVE-2025-71160 and 5 more.