CVE-2026-74715
Received Received - Intake

BPF NetNS Reference Leak in Linux Kernel

Publication date: 2026-08-22

Last updated on: 2026-08-22

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix netns reference imbalance in conntrack kfuncs The opts argument of the BPF conntrack kfuncs can point to a shared map value. __bpf_nf_ct_lookup() and __bpf_nf_ct_alloc_entry() read opts->netns_id separately when acquiring and releasing the network namespace reference. The reference imbalance can occur as follows: CPU 0 CPU 1 read opts->netns_id (-1) skip get_net_ns_by_id() write opts->netns_id (id) read opts->netns_id (id) put_net(net) /* no matching get */ The reverse transition leaks the reference. Repeating the unmatched put can destroy a live namespace and crash later users. The kernel reported: Oops: general protection fault, probably for non-canonical address KASAN: null-ptr-deref in range [0x00000000000000e8-0x00000000000000ef] RIP: 0010:bpf_prog_test_run_xdp+0x52c/0x1700 Call Trace: __sys_bpf+0x1662/0x50c0 __x64_sys_bpf+0x73/0xb0 do_syscall_64+0xf9/0x540 entry_SYSCALL_64_after_hwframe+0x77/0x7f Kernel panic - not syncing: Fatal exception Snapshot every input field of opts with READ_ONCE() before validating or using it. The netns_id snapshot keeps the namespace get/put pair balanced, while the other snapshots keep the remaining options from changing partway through an invocation. The individual reads can still observe an inconsistent combination during a concurrent update, but each selected field value remains stable for that invocation.

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Meta Information

Published
2026-08-22
Last Modified
2026-08-22
Generated
2026-08-22
AI Q&A
2026-08-22
EPSS Evaluated
N/A
NVD
CVE-2026-74715
EUVD
EUVD-2026-64402

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a reference imbalance in BPF conntrack kfuncs. The issue occurs when the opts argument points to a shared map value, leading to mismatched network namespace references. Specifically, reading opts->netns_id separately during acquisition and release can cause a reference leak, potentially destroying a live namespace and crashing the system.

Detection Guidance

This vulnerability is specific to the Linux kernel's BPF conntrack kfuncs and may not have direct detection commands. Monitor kernel logs for general protection faults or null-pointer dereferences related to BPF operations. Check for crashes or panics in kernel logs with commands like dmesg | grep -i 'general protection fault' or journalctl -k | grep -i 'bpf_prog_test_run_xdp'.

Impact Analysis

This vulnerability can cause kernel crashes, including general protection faults and null-pointer dereferences. It may lead to system instability, data corruption, or denial of service. Attackers could exploit this to trigger kernel panics or execute arbitrary code with kernel privileges.

Mitigation Strategies

Apply the latest kernel patches or updates that resolve this issue. If patches are unavailable, avoid using BPF conntrack kfuncs until a fix is applied. Monitor kernel security advisories for updates related to CVE-2026-74715.

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