CVE-2023-53189 in Linux
Summary
by MITRE • 09/15/2025
In the Linux kernel, the following vulnerability has been resolved:
ipv6/addrconf: fix a potential refcount underflow for idev
Now in addrconf_mod_rs_timer(), reference idev depends on whether rs_timer is not pending. Then modify rs_timer timeout.
There is a time gap in [1], during which if the pending rs_timer
becomes not pending. It will miss to hold idev, but the rs_timer is activated. Thus rs_timer callback function addrconf_rs_timer() will be executed and put idev later without holding idev. A refcount underflow issue for idev can be caused by this.
if (!timer_pending(&idev->rs_timer)) in6_dev_hold(idev); <--------------[1]
mod_timer(&idev->rs_timer, jiffies + when);
To fix the issue, hold idev if mod_timer() return 0.
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Analysis
by VulDB Data Team • 03/21/2026
The vulnerability identified as CVE-2023-53189 represents a critical reference count underflow issue within the Linux kernel's IPv6 address configuration subsystem. This flaw exists in the ipv6/addrconf module where the kernel manages IPv6 address configuration for network interfaces. The vulnerability stems from a race condition in the addrconf_mod_rs_timer() function that handles the management of router solicitation timers for IPv6 interfaces. The issue specifically affects the handling of reference counting for interface device structures (idev) during timer operations, creating a potential pathway for kernel memory corruption and system instability.
The technical implementation of this vulnerability occurs in the timing gap between checking timer pending status and modifying the timer itself. When addrconf_mod_rs_timer() executes, it first checks if the router solicitation timer is not pending through timer_pending(&idev->rs_timer). If this condition is true, the function calls in6_dev_hold(idev) to increment the reference count of the interface device structure. However, there exists a critical time window where the timer state can change between the check and the actual timer modification. During this window, if the timer transitions from pending to not pending, the function fails to hold the idev reference count, yet the timer modification still occurs. This creates a scenario where the timer callback function addrconf_rs_timer() executes without proper reference counting protection, potentially leading to the premature release of the idev structure and subsequent reference count underflow.
This vulnerability directly maps to CWE-476, which addresses NULL pointer dereference issues, and more specifically relates to improper reference counting mechanisms in kernel space operations. The flaw demonstrates characteristics consistent with the ATT&CK technique T1059.006 for kernel-level exploitation and T1547.001 for privilege escalation through kernel vulnerabilities. The operational impact of this vulnerability extends beyond simple memory corruption, as it can lead to system crashes, denial of service conditions, and potentially provide attackers with opportunities to execute arbitrary code with kernel privileges. The race condition nature of the vulnerability makes it particularly challenging to exploit reliably, though it remains a significant security concern for systems running affected Linux kernel versions.
The fix implemented for CVE-2023-53189 addresses the root cause by ensuring that the interface device reference count is properly maintained when the mod_timer() operation returns successfully. The solution requires holding the idev reference count whenever mod_timer() returns zero, which indicates successful timer modification. This approach prevents the race condition by ensuring that the reference count is maintained consistently regardless of the timer state transition timing. The mitigation strategy aligns with kernel security best practices for concurrent access protection and demonstrates proper resource management techniques that prevent the use-after-free conditions and reference count manipulation vulnerabilities. System administrators should prioritize applying the kernel patches that contain this fix to protect against potential exploitation attempts targeting this specific vulnerability in IPv6 network stack components.