CVE-2026-12844 in List::SomeUtils::XS
Summary
by MITRE • 06/25/2026
List::SomeUtils::XS versions before 0.59 for Perl have a heap buffer overflow in the pairwise function.
pairwise() collects the values returned by the block into a heap buffer sized to the longer input array, then grows the buffer before each copy with a single quadrupling (alloc <<= 2) instead of a loop. A block call that returns more than four times the current allocation in one invocation outgrows that one quadrupling, and the copy writes past the end of the buffer.
Any caller of pairwise() whose block returns, for a single pair, more than four times the longer input array's length writes past the buffer and corrupts the heap.
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Analysis
by VulDB Data Team • 06/25/2026
The vulnerability in List::SomeUtils::XS versions prior to 0.59 represents a critical heap buffer overflow condition that arises from improper memory management within the pairwise function implementation. This flaw demonstrates a classic memory safety issue where the allocated buffer size does not adequately account for the potential growth of data during processing, creating a scenario where malicious input can trigger memory corruption.
The technical root cause lies in the memory allocation strategy employed by the pairwise function which calculates buffer size based on the longer of two input arrays and then applies a single quadrupling operation to expand the allocation through the expression alloc <<= 2. This approach fails to account for scenarios where a single block invocation might return data that exceeds four times the current buffer capacity, resulting in a single overflow condition that corrupts adjacent heap memory regions.
The operational impact of this vulnerability extends beyond simple memory corruption as it creates opportunities for arbitrary code execution and system compromise. Attackers can craft input data that triggers the specific condition where a block returns more than four times the input array length, causing the function to write past the allocated buffer boundaries and overwrite critical heap metadata or adjacent memory structures. This type of vulnerability aligns with CWE-121 Heap-based Buffer Overflow and represents a serious security risk in environments where untrusted input passes through the pairwise function.
The vulnerability affects any Perl application utilizing List::SomeUtils::XS versions before 0.59 that employ the pairwise function with user-controllable input data, particularly in web applications or systems processing external data feeds. The attack surface expands when considering that many Perl web frameworks and applications rely on third-party modules for array manipulation operations, making this a potential vector for remote code execution in vulnerable environments.
Mitigation strategies should prioritize immediate patching to version 0.59 or later which implements proper memory expansion logic using iterative allocation loops rather than single quadrupling operations. Additionally, system administrators should implement input validation measures to limit the size of data processed through the pairwise function and consider runtime protections such as address space layout randomization and stack canaries. The vulnerability demonstrates the importance of robust memory management practices in interpreted languages where dynamic memory allocation occurs frequently during program execution, aligning with ATT&CK technique T1059.007 for script-based exploitation and T1499.004 for network infiltration through vulnerable components.
Security monitoring should focus on detecting unusual memory allocation patterns and heap corruption indicators when processing data through the pairwise function, while developers should implement defensive programming practices including bounds checking, proper error handling, and regular security code reviews to prevent similar buffer overflow conditions in custom implementations of array processing functions.