CVE-2026-74403 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
crypto: ccp - Check for page allocation failure correctly in TIO
Sashiko notes:
> if __snp_alloc_firmware_pages() returns NULL under memory pressure, is it > safe to pass it directly to page_address()? > > On architectures without HASHED_PAGE_VIRTUAL, page_address(NULL) might > compute a deterministic but invalid, non-zero virtual address. The > subsequent if (tio_status) check would then evaluate to true, and > sev_tsm_init_locked() would dereference the invalid pointer.
Indeed, page_address(NULL) will return non-NULL garbage here. Fix this by checking the page allocation itself for NULL, not the resulting virtual address.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability resides in the Linux kernel's cryptographic component ccp driver, specifically within the TIO (Trusted I/O) subsystem that handles Secure Encrypted Virtualization (SEV) functionality. This issue represents a critical memory management flaw that can lead to system instability and potential security implications. The problem manifests when the __snp_alloc_firmware_pages() function fails to allocate memory pages under memory pressure conditions, returning NULL to indicate allocation failure. However, the subsequent code path incorrectly passes this NULL value directly to the page_address() function without proper validation.
The technical flaw stems from improper error handling in memory allocation sequences where the driver fails to distinguish between successful page allocation and allocation failure scenarios. When memory pressure forces __snp_alloc_firmware_pages() to return NULL, the code continues processing by passing this null pointer to page_address(), which on certain architectures lacking HASHED_PAGE_VIRTUAL support returns a deterministic but invalid non-zero virtual address. This behavior violates fundamental safety principles in kernel programming where null pointer dereferences must be prevented before any memory access operations occur.
The operational impact of this vulnerability extends beyond simple system crashes or hangs, as it creates potential attack vectors for privilege escalation and denial of service conditions. The flaw allows an attacker to potentially manipulate the kernel's memory management subsystem through controlled allocation failures, leading to invalid memory references that could be exploited to corrupt kernel data structures or execute arbitrary code with kernel privileges. This vulnerability particularly affects systems running SEV-enabled virtualization environments where the TIO subsystem is actively utilized for secure memory operations.
The resolution requires implementing proper null pointer validation before invoking page_address() functions, ensuring that allocation failures are handled gracefully and explicitly checked for before any virtual address computation occurs. This fix aligns with established security practices outlined in CWE-476 which addresses null pointer dereference vulnerabilities, and corresponds to ATT&CK technique T1068 related to privilege escalation through kernel exploits. Organizations should prioritize immediate patch deployment and verify that all SEV-enabled systems have been updated to prevent exploitation of this memory management weakness.
The vulnerability demonstrates the critical importance of proper error handling in kernel space programming where resource allocation failures must be explicitly checked and handled before any subsequent operations that depend on successful allocation outcomes. This particular flaw highlights the complexity of memory management in virtualized environments and underscores the need for comprehensive testing under memory pressure conditions to identify potential race conditions and allocation failure scenarios that could compromise system stability and security.