CVE-2026-81693 in openssl_encrypt
Summary
by MITRE • 08/27/2026
openssl_encrypt before 1.4.9 fails to validate the total field from QR JSON payloads before materializing ranges. Attackers can supply crafted QR images with extremely large total values to trigger unbounded memory allocation and cause denial of service through out-of-memory conditions.
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Analysis
by VulDB Data Team • 08/27/2026
The vulnerability in openssl_encrypt prior to version 1.4.9 represents a critical input validation failure within the processing logic for Quick Response, commonly known as QR code payloads. Specifically, the application fails to perform adequate boundary checks on the total field contained within JSON-based QR data structures before initiating memory allocation routines. This oversight allows an attacker to inject maliciously crafted QR images that encode extremely large numerical values in the total field. When the system attempts to materialize ranges based on this unvalidated input, it proceeds without verifying whether the requested resource consumption is feasible or safe for the host environment.
From a technical perspective, this flaw constitutes a classic case of improper input validation leading to an integer overflow or excessive allocation scenario. The software relies on the total field value to determine the size of memory buffers required for processing the QR payload data. Because there are no upper limits enforced on this parameter before materialization occurs, supplying a sufficiently large number causes the application to request more memory than is available in the system heap. This results in an unbounded memory allocation attempt which inevitably fails or exhausts all available resources depending on how the underlying operating system handles such requests.
The operational impact of this vulnerability is primarily focused on availability rather than confidentiality or integrity, as it enables a denial of service attack vector. An attacker can remotely trigger this condition by presenting a specially constructed QR image to any component that processes these payloads using the affected version of openssl_encrypt. The consequence is an out-of-memory condition that typically leads to application crashes, process termination, or system-wide instability if critical services are impacted. This effectively renders the service unavailable to legitimate users until the compromised instance is restarted and memory resources are reclaimed by the operating system scheduler.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-400 which describes uncontrolled resource consumption due to insufficient control over allocated resources. Furthermore, in the context of the MITRE ATT&CK framework, this behavior corresponds to techniques associated with Denial of Service attacks where adversaries aim to disrupt service availability by exhausting system resources rather than compromising data integrity or accessing unauthorized information directly. The lack of pre-allocation validation is a fundamental security design flaw that should have been addressed during the development phase through rigorous input sanitization and range checking protocols.
To mitigate this risk, organizations must immediately upgrade openssl_encrypt to version 1.4.9 or later where these validation checks have presumably been implemented. In addition to upgrading software components, developers should implement defense-in-depth strategies by enforcing strict schema validations on all incoming JSON payloads regardless of their source trust level. Input sanitization routines should explicitly check that numeric fields such as total values fall within expected operational bounds before they are passed to memory allocation functions. Monitoring systems should also be configured to detect abnormal spikes in memory usage associated with QR processing modules, allowing for automated remediation or alerting when potential exploitation attempts are detected.