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

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel 2.6.20版本存在安全漏洞，该漏洞源于netfilter nf_conntrack的expectfn清理问题，当NAT帮助程序（如nf_nat_h323）卸载后，预期连接到达时会导致空指针取消引用。

AI Predicted 7.8 Difficulty: Moderate EPSS 0.12% · P2

Possible ATT&CK Techniques 1 AI

T1211 · Exploitation for Stealth

Affected Version Matrix 14

VendorProduct Version RangeStatus
Linux Linux f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4< fbfde85308b99938a6092c48753214d190ece48d affected
f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4< 29d8cc44bbdf7b83a1929912214afe6643c1b4f1 affected
f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4< f92c90a2a3e6ff6f9f7fe88fde9004b4ca8f956d affected
f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4< 9d017671dcfcec23321fb7962dea624f9e71ddb1 affected
f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4< bf8c0b5dd203be94c2ad50e264cec19267c6bd39 affected
f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4< c3009418f9fa1dcb3eb86f4d8c92583537b5faa3 affected
2.6.20 affected
< 2.6.20 unaffected
… +6 more rows
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I. Basic Information for CVE-2026-53349

Vulnerability Information
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Vulnerability Title
netfilter: nf_conntrack: destroy stale expectfn expectations on unregister
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel 2.6.20版本存在安全漏洞，该漏洞源于netfilter nf_conntrack的expectfn清理问题，当NAT帮助程序（如nf_nat_h323）卸载后，预期连接到达时会导致空指针取消引用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 ~ fbfde85308b99938a6092c48753214d190ece48d -
Linux Linux 2.6.20 -

II. Public POCs for CVE-2026-53349

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III. Intelligence Information for CVE-2026-53349

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Patches & Fixes for CVE-2026-53349 (5)

Same Patch Batch · Linux · 2026-07-01 · 31 CVEs total

CVE-2026-53355 9.8 CRITICAL net: rds: clear i_sends on setup unwind
CVE-2026-53354 8.8 HIGH arm64: errata: Mitigate TLBI errata on various Arm CPUs
CVE-2026-53341 7.8 HIGH fhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh()
CVE-2026-53356 7.8 HIGH drm/i915/gem: Fix phys BO pread/pwrite with offset
CVE-2026-53329 7.0 HIGH drm/amd/display: Use krealloc_array() in dal_vector_reserve()
CVE-2026-53343 ARM: 9475/1: entry: use byte load for KASAN VMAP stack shadow
CVE-2026-53326 debugobjects: Don't call fill_pool() in early boot hardirq context
CVE-2026-53328 sched_ext: Don't warn on NULL cgrp_moving_from in scx_cgroup_move_task()
CVE-2026-53353 hsr: Remove WARN_ONCE() in hsr_addr_is_self().
CVE-2026-53330 drm/amd/display: Fix out-of-bounds read in dp_get_eq_aux_rd_interval()
CVE-2026-53352 signal: clear JOBCTL_PENDING_MASK for caller in zap_other_threads()
CVE-2026-53351 riscv/ptrace: Use USER_REGSET_NOTE_TYPE for REGSET_CFI
CVE-2026-53350 ASoC: wm_adsp: Fix NULL dereference when removing firmware controls
CVE-2026-53348 ASoC: SDCA: fix NULL pointer dereference in sdca_dev_unregister_functions
CVE-2026-53346 rust: arm64: set uwtable llvm module flag for CONFIG_UNWIND_TABLES
CVE-2026-53347 drm/virtio: Fix driver removal with disabled KMS
CVE-2026-53344 pinctrl: mcp23s08: Initialize mcp->dev and mcp->addr before regmap init
CVE-2026-53345 KVM: Don't WARN if memory is dirtied without a vCPU when the VM is dying
CVE-2026-53342 arm64: mm: call pagetable dtor when freeing hot-removed page tables
CVE-2026-53327 debugobjects: Do not fill_pool() if pi_blocked_on

Showing top 20 of 31 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-53349

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