CVE-2026-64533

In the Linux kernel, the following vulnerability has been resolved:

fs/ntfs3: validate lcns_follow in log_replay conversion

log_replay() converts DIR_PAGE_ENTRY_32 records into DIR_PAGE_ENTRY records when replaying version 0 restart tables.

During this conversion, the memmove() length is derived directly from the on-disk lcns_follow field:

memmove(&dp->vcn, &dp0->vcn_low,
	2 * sizeof(u64) +
			le32_to_cpu(dp->lcns_follow) * sizeof(u64));

check_rstbl() validates restart table structure, but does not constrain per-entry lcns_follow values relative to the entry size. A malformed filesystem image can provide an oversized lcns_follow value, causing the conversion memmove() to access memory beyond the bounds of the allocated restart table buffer.

The same field is later used to bound iteration over page_lcns[], so validating lcns_follow during conversion also prevents downstream out-of-bounds access from the same malformed metadata.

Compute the maximum valid lcns_follow from the already-validated restart table entry size and reject entries that exceed this bound. Reuse the existing t16/t32 scratch variables already declared in log_replay() to avoid introducing new declarations.

[almaz.alexandrovich@paragon-software.com: fixed the conflicts]

Weakness

The product writes data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.

• Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.

• Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.

• D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.

• Consider adhering to the following rules when allocating and managing an application’s memory:

• Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

• Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.

• For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

• Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.

• For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].

References

• https://git.kernel.org/stable/c/159f694d682e4215b3822ae31ed3a4631628fe55
• https://git.kernel.org/stable/c/32b9f8733feb241627fa5f564b1a99b5cae974c5
• https://git.kernel.org/stable/c/57c071e2c4f30b9c6f5aacb6679aab1269fbae99
• https://git.kernel.org/stable/c/6a4c53a2e26a865565bd6a460961e8d6fcb32329
• https://git.kernel.org/stable/c/7adb38279812c9c06b0e3fa7382f4d7887f3fa2d
• https://git.kernel.org/stable/c/ca343a99806b4fc8e27c48f08be3445c5fcd1445
• https://git.kernel.org/stable/c/ddfc8683e1a627dbf1b83bacf8961443dd654258