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The vulnerability is a memory leak in the Linux kernel’s device tree (of) unittest module. In the function unittest_data_add(), memory is allocated for the variable unittest_data. Subsequently, the function `of_resolve_phandles()` is called. If `of_resolve_phandles()` fails and returns an error, the function `unittest_data_add()` exits without freeing the previously allocated memory for unittest_data. This creates a scenario where a small amount of kernel memory is not released, remaining allocated but unused until the system is rebooted. The fix implemented by the kernel developers replaces the manual error handling with a scope-based cleanup helper, __free(kfree). This modern C language feature ensures that `unittest_data` is automatically freed when it goes out of scope, covering all error paths without needing explicit `goto` statements. For the success path, the function `retain_and_null_ptr()` is used to transfer ownership of the memory to the device tree subsystem, preventing any double-free issues that could occur from the automatic cleanup.
Platform: Linux Kernel
Version: 3.18 to 6.18.6, and versions up to 6.19
Vulnerability: Memory Leak
Severity: Low (No CVSS assigned)
date: 14 Feb 2026
Prediction: Patched 02 Jan 2026
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The vulnerability `CVE-2026-23137` is a classical software bug related to improper resource management. It resides specifically in the Device Tree (OF – Open Firmware) unittesting code within the Linux kernel. The primary risk is not a direct system compromise but a gradual degradation of system resources. Over time, repeated triggering of the error path in `unittest_data_add()` could lead to memory exhaustion, potentially causing system instability or denial-of-service conditions on systems that heavily utilize or test device tree functionalities. The flaw was introduced with commit `2eb46da2a760` (“of/selftest: Use the resolver to fixup phandles”) and affects kernel versions from v3.18 onwards. The fix was applied to the mainline kernel on January 2, 2026.
Exploit:
As of the patch date, there is no public exploit code for this vulnerability. The flaw is a standard memory leak triggered by a specific error condition within a kernel testing module. Exploiting this would require an attacker to have the ability to influence the device tree or the unittesting process to cause the `of_resolve_phandles()` function to fail, which is a non-trivial task in a production environment. The memory leak itself is not directly exploitable for code execution or privilege escalation. It is a denial-of-service vulnerability at best.
Protection from this CVE
Protection is achieved by updating the Linux kernel to a version that includes the fix. The fix was applied via two specific commits:
`f09b0f705bd7197863b90256ef533a6414d1db2c`
`235a1eb8d2dcc49a6cf0a5ee1aa85544a5d0054b`
System administrators should ensure their kernel is updated to a version containing these commits. This typically means updating to a kernel version newer than 6.18.6 or applying the relevant stable kernel patches provided by your Linux distribution.
Bash commands to verify kernel version:
Check the current running kernel version uname -r On Debian/Ubuntu, check available updates sudo apt update && apt list --upgradable | grep linux-image On RHEL/CentOS/Fedora, check available updates sudo dnf check-update kernel
Check if the fix is present in your kernel source (if you have it):
Go to your kernel source directory and use git log git log --oneline drivers/of/unittest.c | grep -E "f09b0f70|235a1eb8" Or use a more general search for the commit message git log --grep="unittest: Fix memory leak in unittest_data_add()"
Impact
The impact of CVE-2026-23137 is considered low. It is a memory leak confined to a specific error path in a driver testing subsystem. For an average end-user or server administrator not actively developing or testing device tree changes, the likelihood of triggering this bug is minimal. The primary consequence is a slow, undetectable leak of kernel memory, which could contribute to system instability over very long periods of uptime. The vulnerability does not allow for privilege escalation, information disclosure, or remote code execution.
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Sources:
Reported By: nvd.nist.gov
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