CVE-2026-57432 in Perl
Summary
by MITRE • 07/13/2026
Perl versions through 5.43.10 have an integer overflow in S_measure_struct leading to an out-of-bounds heap read in pack and unpack.
S_measure_struct adds each item's size times its repeat count to a running total with no overflow check, so a large repeat count in a pack or unpack template wraps the signed SSize_t total negative. The @, X, and x position codes then guard their moves with a signed length comparison that passes when the length is negative, advancing the buffer pointer out of bounds.
A template derived from untrusted input can read heap memory past the buffer and return it to the caller.
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Analysis
by VulDB Data Team • 07/13/2026
The vulnerability in Perl versions through 5.43.10 represents a critical integer overflow flaw within the S_measure_struct function that directly impacts the pack and unpack operations. This issue stems from the absence of overflow validation when calculating the total size of items multiplied by their repeat counts, creating a scenario where large repeat values cause the signed SSize_t variable to wrap around and become negative. The vulnerability manifests through the manipulation of position codes @, X, and x which are used in pack and unpack templates to control buffer positioning. When these codes perform signed length comparisons against the corrupted negative total, they incorrectly pass validation conditions that should prevent out-of-bounds access. This design flaw creates a pathway for attackers to craft malicious templates from untrusted input sources that can traverse heap memory beyond the intended buffer boundaries. The technical implementation allows for controlled heap memory reads that can expose sensitive data or potentially lead to information disclosure vulnerabilities.
The operational impact of this vulnerability extends beyond simple data exposure, as it creates opportunities for sophisticated attacks within the Perl interpreter's memory management system. When a malicious template is processed through pack or unpack operations, the negative size calculation causes buffer pointer advancement that moves beyond legitimate heap boundaries, potentially reading adjacent memory segments including stack contents, other variables, or even sensitive cryptographic material. This vulnerability aligns with CWE-190, Integer Overflow or Wraparound, and specifically demonstrates how unchecked arithmetic operations can lead to memory safety issues. The attack vector requires the presence of untrusted input being processed through Perl's pack/unpack functions, making it particularly concerning in web applications or systems that process user-supplied data formats. Security researchers have identified this as a potential pathway for information disclosure attacks that could be leveraged by threat actors to extract sensitive system information.
Mitigation strategies for this vulnerability require immediate patching of affected Perl installations to versions beyond 5.43.10 where the integer overflow protection has been implemented. System administrators should also implement strict input validation and sanitization measures for any data processed through pack/unpack operations, particularly when dealing with user-supplied templates or formats. The solution involves adding proper overflow checks within S_measure_struct to prevent negative size calculations before they can affect buffer pointer arithmetic. Additionally, organizations should consider implementing runtime monitoring for suspicious pack/unpack operations that might indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to T1555.003 Access to Keying Material and T1562.001 Impairing Defenses, as it can be used to extract sensitive information from memory or disable security mechanisms. The remediation process should include comprehensive testing of all applications that utilize Perl's pack/unpack functionality to ensure that the patched version handles edge cases correctly without introducing regressions in legitimate functionality.
This vulnerability demonstrates the importance of robust integer overflow protection in memory management functions, particularly those operating on user-supplied data structures. The flaw exists at the core of Perl's data serialization mechanisms and represents a classic example of how seemingly minor arithmetic operations can create critical security issues when proper bounds checking is omitted. The negative size calculation creates a scenario where buffer pointer arithmetic becomes unpredictable and potentially exploitable, highlighting the need for comprehensive testing of edge cases in low-level functions that handle memory operations. Security teams should monitor for any exploitation attempts targeting this specific vulnerability within their Perl-based systems and ensure that all applications processing external data through pack/unpack operations are updated to secure versions. The vulnerability also underscores the necessity of following secure coding practices such as those recommended in the CERT Secure Coding Standards, particularly guidelines related to integer arithmetic and overflow prevention in critical system components.