CVE-2026-53349
netfilter: 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.
INFO
Published Date :
July 1, 2026, 2:16 p.m.
Last Modified :
July 22, 2026, 7:15 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update the Linux kernel to the patched version.
- Ensure module removal handles pending expectations correctly.
- Load and test NAT helpers after applying patches.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-53349.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-53349 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-53349
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-53349 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-53349 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jul. 22, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Added CWE NVD-CWE-noinfo Added CPE Configuration OR *cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc4:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.2 up to (excluding) 6.6.143 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.13 up to (excluding) 6.18.36 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.7 up to (excluding) 6.12.94 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.19 up to (excluding) 7.0.13 *cpe:2.3:o:linux:linux_kernel:7.1:rc5:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc6:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:7.1:rc7:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 2.6.20 up to (excluding) 6.1.176 Added Reference Type kernel.org: https://git.kernel.org/stable/c/29d8cc44bbdf7b83a1929912214afe6643c1b4f1 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/9d017671dcfcec23321fb7962dea624f9e71ddb1 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/bf8c0b5dd203be94c2ad50e264cec19267c6bd39 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/c3009418f9fa1dcb3eb86f4d8c92583537b5faa3 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/f92c90a2a3e6ff6f9f7fe88fde9004b4ca8f956d Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/fbfde85308b99938a6092c48753214d190ece48d Types: Patch -
New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Jul. 01, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': 'f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4', 'lessThan': 'fbfde85308b99938a6092c48753214d190ece48d', 'versionType': 'git'}, {'status': 'affected', 'version': 'f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4', 'lessThan': '29d8cc44bbdf7b83a1929912214afe6643c1b4f1', 'versionType': 'git'}, {'status': 'affected', 'version': 'f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4', 'lessThan': 'f92c90a2a3e6ff6f9f7fe88fde9004b4ca8f956d', 'versionType': 'git'}, {'status': 'affected', 'version': 'f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4', 'lessThan': '9d017671dcfcec23321fb7962dea624f9e71ddb1', 'versionType': 'git'}, {'status': 'affected', 'version': 'f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4', 'lessThan': 'bf8c0b5dd203be94c2ad50e264cec19267c6bd39', 'versionType': 'git'}, {'status': 'affected', 'version': 'f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4', 'lessThan': 'c3009418f9fa1dcb3eb86f4d8c92583537b5faa3', 'versionType': 'git'}], 'programFiles': ['include/net/netfilter/nf_conntrack_helper.h', 'net/ipv4/netfilter/nf_nat_h323.c', 'net/netfilter/nf_conntrack_helper.c', 'net/netfilter/nf_nat_core.c', 'net/netfilter/nf_nat_sip.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '2.6.20'}, {'status': 'unaffected', 'version': '0', 'lessThan': '2.6.20', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.1.176', 'versionType': 'semver', 'lessThanOrEqual': '6.1.*'}, {'status': 'unaffected', 'version': '6.6.143', 'versionType': 'semver', 'lessThanOrEqual': '6.6.*'}, {'status': 'unaffected', 'version': '6.12.94', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.36', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.0.13', 'versionType': 'semver', 'lessThanOrEqual': '7.0.*'}, {'status': 'unaffected', 'version': '7.1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['include/net/netfilter/nf_conntrack_helper.h', 'net/ipv4/netfilter/nf_nat_h323.c', 'net/netfilter/nf_conntrack_helper.c', 'net/netfilter/nf_nat_core.c', 'net/netfilter/nf_nat_sip.c'], 'defaultStatus': 'affected'}] Added 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. Added Reference https://git.kernel.org/stable/c/29d8cc44bbdf7b83a1929912214afe6643c1b4f1 Added Reference https://git.kernel.org/stable/c/9d017671dcfcec23321fb7962dea624f9e71ddb1 Added Reference https://git.kernel.org/stable/c/bf8c0b5dd203be94c2ad50e264cec19267c6bd39 Added Reference https://git.kernel.org/stable/c/c3009418f9fa1dcb3eb86f4d8c92583537b5faa3 Added Reference https://git.kernel.org/stable/c/f92c90a2a3e6ff6f9f7fe88fde9004b4ca8f956d Added Reference https://git.kernel.org/stable/c/fbfde85308b99938a6092c48753214d190ece48d