CVE-2025-38630 in Linux
Summary
by MITRE • 08/22/2025
In the Linux kernel, the following vulnerability has been resolved:
fbdev: imxfb: Check fb_add_videomode to prevent null-ptr-deref
fb_add_videomode() can fail with -ENOMEM when its internal kmalloc() cannot allocate a struct fb_modelist. If that happens, the modelist stays empty but the driver continues to register. Add a check for its return value to prevent poteintial null-ptr-deref, which is similar to the commit 17186f1f90d3 ("fbdev: Fix do_register_framebuffer to prevent null-ptr-deref in fb_videomode_to_var").
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Analysis
by VulDB Data Team • 05/28/2026
The vulnerability CVE-2025-38630 resides within the Linux kernel's framebuffer device subsystem, specifically affecting the imxfb driver implementation. This issue represents a classic null pointer dereference vulnerability that occurs during the framebuffer registration process. The flaw manifests when the fb_add_videomode() function encounters memory allocation failure during the kmalloc() operation for struct fb_modelist allocation. When this memory allocation fails with -ENOMEM error code, the function returns an error condition but the driver continues execution without proper error handling, creating a dangerous state where the modelist remains empty yet the registration process proceeds.
The technical implementation flaw stems from inadequate error checking in the framebuffer device initialization sequence. The imxfb driver calls fb_add_videomode() to populate video mode information but fails to validate the return value of this function before proceeding with the framebuffer registration. This pattern creates a potential null pointer dereference scenario where subsequent operations might attempt to access the uninitialized or improperly allocated modelist structure. The vulnerability is particularly concerning because it occurs in the kernel's core device management layer where improper error handling can lead to system instability or potential privilege escalation.
From an operational impact perspective, this vulnerability could result in system crashes or unpredictable behavior when the framebuffer device attempts to register under memory pressure conditions. The attack surface is primarily limited to systems utilizing the imxfb framebuffer driver, typically found in embedded systems or devices with specific graphics hardware configurations. However, the consequences extend beyond simple system instability as kernel memory corruption from null pointer dereferences can potentially be exploited to escalate privileges or cause denial of service conditions. This vulnerability aligns with CWE-476 which specifically addresses null pointer dereference conditions in software implementations.
The mitigation strategy involves implementing proper error checking following the fb_add_videomode() call, similar to the established pattern used in commit 17186f1f90d3 that addressed comparable issues in the fbdev subsystem. This approach requires the driver to verify the return value of fb_add_videomode() and abort the registration process if memory allocation fails. The fix pattern demonstrates adherence to secure coding practices outlined in the ATT&CK framework's defensive techniques for preventing kernel-level memory corruption vulnerabilities. System administrators should prioritize applying the kernel patch that implements this validation check, particularly in embedded environments where memory constraints increase the likelihood of allocation failures. The solution follows industry best practices for kernel security and aligns with the principle of fail-fast error handling mechanisms that prevent cascading failures in critical system components.