CVE-2026-53349netfilter: nf_conntrack: destroy stale expectfn expectations on unregister

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack: destroy stale expectfn expectations on unregister NAT helpers such as nf_nat_h323 store a raw pointer to module text in exp->expectfn (e.g. ip_nat_q931_expect). nf_ct_helper_expectfn_unregister() only unlinks the callback descriptor and never walks the expectation table, so an expectation pending at module removal survives with a dangling exp->expectfn into freed module text. When the expected connection arrives, init_conntrack() invokes exp->expectfn(), now a stale pointer into the unloaded module. Reproduced on a KASAN build by loading the H.323 helpers, creating a Q.931 expectation, unloading nf_nat_h323, then connecting to the expected port: Oops: int3: 0000 [#1] SMP KASAN NOPTI RIP: 0010:0xffffffffa06102d1 init_conntrack.isra.0 (net/netfilter/nf_conntrack_core.c:1862) nf_conntrack_in (net/netfilter/nf_conntrack_core.c:2049) ipv4_conntrack_local (net/netfilter/nf_conntrack_proto.c:223) nf_hook_slow (net/netfilter/core.c:619) __ip_local_out (net/ipv4/ip_output.c:120) __tcp_transmit_skb (net/ipv4/tcp_output.c:1715) tcp_connect (net/ipv4/tcp_output.c:4374) tcp_v4_connect (net/ipv4/tcp_ipv4.c:345) __sys_connect (net/socket.c:2167) Modules linked in: nf_conntrack_h323 [last unloaded: nf_nat_h323] Reaching the dangling state requires CAP_SYS_MODULE in the initial user namespace to remove a NAT helper that still has live expectations, so this is a robustness fix; leaving an expectation pointing at freed text is wrong regardless. Add nf_ct_helper_expectfn_destroy(), which walks the expectation table and drops every expectation whose ->expectfn matches the descriptor being torn down. Call it from each NAT helper's exit path after the existing RCU grace period, so no expectation outlives the code it points at and no extra synchronize_rcu() is introduced. With the fix, the same reproducer runs to completion without the Oops.

Timeline

Scores

EPSS (exploitation in 30 days)

0.12% · top 98% of all CVEs (14 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.

Affected products

• Linux · Linux

  • affected f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 – < fbfde85308b99938a6092c48753214d190ece48d
  • affected f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 – < 29d8cc44bbdf7b83a1929912214afe6643c1b4f1
  • affected f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 – < f92c90a2a3e6ff6f9f7fe88fde9004b4ca8f956d
  • affected f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 – < 9d017671dcfcec23321fb7962dea624f9e71ddb1
  • affected f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 – < bf8c0b5dd203be94c2ad50e264cec19267c6bd39
  • affected f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 – < c3009418f9fa1dcb3eb86f4d8c92583537b5faa3

• Linux · Linux

  • affected 2.6.20
  • unaffected < 2.6.20
  • unaffected 6.1.176 – ≤ 6.1.*
  • unaffected 6.6.143 – ≤ 6.6.*
  • unaffected 6.12.94 – ≤ 6.12.*
  • unaffected 6.18.36 – ≤ 6.18.*
  • unaffected 7.0.13 – ≤ 7.0.*
  • unaffected 7.1 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-40983 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-53349](https://cveledger.app/badge/CVE-2026-53349.svg)](https://cveledger.app/cve/CVE-2026-53349)

Record last updated 6 Nov 2026, 16:34 UTC.