CVE-2026-64245 in Linux
Summary
by MITRE • 07/24/2026
In the Linux kernel, the following vulnerability has been resolved:
fbdev: modedb: fix a possible UAF in fb_find_mode()
If mode_option is NULL, it is assigned from mode_option_buf:
if (!mode_option) {
fb_get_options(NULL, &mode_option_buf); mode_option = mode_option_buf; }
Later, name is assigned from mode_option:
const char *name = mode_option;
However, mode_option_buf is freed before name is no longer used:
kfree(mode_option_buf);
while name is still accessed by:
if ((name_matches(db[i], name, namelen) ||
Since name aliases mode_option_buf, this may result in a use-after-free.
Fix this by extending the lifetime of mode_option_buf until the end of the function by using scope-based resource management for cleanup.
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Analysis
by VulDB Data Team • 07/24/2026
The vulnerability described represents a use-after-free condition in the Linux kernel's framebuffer subsystem, specifically within the fb_find_mode() function located in the fbdev modedb component. This issue arises from improper memory management where a buffer allocated for mode option parsing is freed before all references to its contents are completed. The flaw occurs when the mode_option parameter is NULL, triggering the assignment of mode_option_buf to mode_option, followed by immediate freeing of mode_option_buf without ensuring that all dependent references have been resolved.
The technical implementation involves a classic memory safety issue where the variable name becomes an alias for the freed memory location through the assignment const char *name = mode_option; after mode_option has been set to point to mode_option_buf. This creates a scenario where the fb_find_mode() function attempts to access the freed memory region through the name parameter during the name_matches() comparison operation, leading to potential system instability or privilege escalation opportunities. The vulnerability is categorized under CWE-416 as Use After Free, which represents one of the most critical classes of memory safety issues in kernel space programming.
The operational impact of this vulnerability extends beyond simple memory corruption, as it could potentially allow malicious actors to exploit the use-after-free condition for privilege escalation or denial-of-service attacks against systems running affected Linux kernels. Attackers could manipulate input parameters to trigger the specific code path where mode_option is NULL, causing the kernel to allocate and subsequently free mode_option_buf before all references are resolved. The timing of the memory deallocation relative to the function's execution flow creates a window where the freed memory can be accessed, potentially leading to arbitrary code execution or system crashes.
The fix implemented addresses this vulnerability through proper scope-based resource management that extends the lifetime of mode_option_buf until the conclusion of the fb_find_mode() function execution. This approach ensures that all references to the buffer contents remain valid throughout the entire function lifecycle, preventing the premature deallocation that previously led to the use-after-free condition. The solution aligns with secure coding practices recommended in the Linux kernel security guidelines and adheres to the principles outlined in the ATT&CK framework's defensive techniques for memory corruption mitigation. By maintaining proper resource lifetime management, the implementation prevents access to freed memory structures while preserving the intended functionality of the framebuffer mode detection mechanism.
This vulnerability highlights the critical importance of careful memory management in kernel space code where improper resource handling can lead to severe security implications. The fix demonstrates how scope-based cleanup mechanisms provide robust protection against use-after-free vulnerabilities by ensuring that allocated resources remain accessible for the duration of their intended use within function contexts, thereby maintaining system stability and preventing potential exploitation vectors that could compromise the integrity of Linux systems running affected kernel versions.