CVE-2026-74630
Received Received - Intake

Use-After-Free in Linux Kernel IPv6 Networking

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: ipv6: prevent in6_dev_get() from resurrecting inet6_dev in6_dev_get() reads dev->ip6_ptr under RCU and then unconditionally increments its refcount. Device teardown can clear the pointer and drop the last reference between these operations. The increment then resurrects an object whose RCU free has already been queued, so callers can use it after it is freed. Use refcount_inc_not_zero() and return NULL when the object has already reached zero. RCU keeps the memory accessible through the attempted reference acquisition, and a successful increment pins the object for the caller. An independent run on the exact unpatched 6f5156d7a31a (v7.2-rc3) kernel reproduced the invalid reference acquisition as UID 1000: refcount_t: addition on 0; use-after-free. ip6_mc_source+0xef4/0x17e0 It was followed by the corresponding reference underflow in ip6_mc_source(). The supplied trace from the same unpatched revision additionally shows the access after the RCU read-side section ends: BUG: KASAN: slab-use-after-free in mutex_lock+0x76/0xe0 Write of size 8 at addr ffff888015b50240 by task poc/1219 Bug found and triaged by OpenAI Security Research and validated by Trail of Bits.

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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-2026-74630
EUVD
EUVD-2026-64567

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel From 7.2-rc3 (inc)

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Exploitability

CWE
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a use-after-free vulnerability in the Linux kernel's IPv6 networking code. The issue occurs in the in6_dev_get() function, which incorrectly increments a reference count on a network device object that may have already been freed. This happens because the function reads a pointer under RCU (Read-Copy-Update) protection but then unconditionally increments the reference count without checking if the object is still valid.

Detection Guidance

This vulnerability is specific to the Linux kernel and requires kernel-level detection. Check if your system is running a vulnerable kernel version by running: uname -a. If the kernel version is before the patched commit, the system may be affected. Monitor kernel logs for slab-use-after-free errors or refcount_t warnings.

Impact Analysis

This vulnerability could allow an attacker with local access to cause a kernel crash or execute arbitrary code with elevated privileges. It may lead to system instability, denial of service, or potential privilege escalation if exploited successfully.

Mitigation Strategies

Update the Linux kernel to a version that includes the fix for this vulnerability. If immediate patching is not possible, restrict access to untrusted users and avoid running untrusted code. Monitor for unusual kernel errors or crashes.

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