CVE-2026-81696 in openssl_encrypt
Summary
by MITRE • 08/27/2026
openssl_encrypt versions before 1.4.9 fail to sanitize terminal control characters in file metadata printed by the info command. Attackers can craft malicious files containing escape sequences to repaint terminal output and forge verification information displayed to users.
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Analysis
by VulDB Data Team • 08/27/2026
The vulnerability identified in openssl_encrypt prior to version 1.4.9 represents a significant input validation failure within the application's informational reporting mechanism. Specifically, the info command fails to properly sanitize or filter control characters embedded within file metadata fields before they are rendered to the terminal interface. This oversight allows raw escape sequences and other non-printable ASCII control codes to pass through the output pipeline directly into the user's display environment without any form of escaping or neutralization. In modern computing environments, particularly those utilizing ANSI-compatible terminals, these control characters carry specific instructions for cursor movement, color changes, text styling, and screen clearing rather than representing visible data content.
This technical flaw creates a vector for terminal injection attacks, often categorized under the broader umbrella of command injection or output manipulation vulnerabilities. By crafting malicious files that contain carefully constructed escape sequences within their metadata attributes, an attacker can manipulate how the terminal renders subsequent information. The primary operational impact involves the potential to repaint parts of the terminal screen in unexpected ways. This capability allows for visual spoofing techniques where the displayed verification information can be overlaid or replaced with deceptive content. For instance, an attacker could use these sequences to hide legitimate security warnings and replace them with fabricated success messages, thereby misleading users into believing that a file has passed integrity checks when it may not have.
From a threat modeling perspective, this vulnerability aligns closely with CWE-16 regarding the inclusion of unintended functionality within software output, specifically focusing on improper neutralization of special elements used in an output context. It also relates to CWE-79 if one considers that the manipulation affects the user's perception and trust in the application's feedback loop, although it is not a direct code execution vector like Cross-Site Scripting. In terms of adversary tactics, this behavior mirrors techniques found in the MITRE ATT&CK framework under T1608, which involves Stage Resources such as implanting or modifying files to facilitate further attacks. The specific method of using terminal escape codes for deception falls under T1537, specifically related to communication through alternative protocols or interfaces that may bypass standard security monitoring if those monitors do not account for visual manipulation in interactive sessions.
The severity of this issue is compounded by the social engineering aspect it enables. Users relying on openssl_encrypt for cryptographic verification are likely to trust the output displayed during an info command as a source of truth regarding file integrity and metadata accuracy. When malicious actors can forge these verification messages, they undermine the fundamental security guarantee provided by the tool. This could lead users to proceed with executing or trusting compromised files because the interface falsely indicates that no anomalies were detected. The risk is particularly acute in automated scripts where terminal output might be parsed for status indicators, although the primary impact here remains focused on interactive user deception through visual manipulation of the console display.
Mitigation strategies must focus primarily on upgrading to version 1.4.9 or later, which addresses this sanitization gap by implementing proper filtering mechanisms for control characters in metadata fields before they are sent to standard output. For organizations unable to immediately upgrade, defensive coding practices should be employed if custom wrappers around the library exist. These wrappers should explicitly strip all non-printable ASCII characters from file metadata prior to display or logging. Additionally, security awareness training can help users recognize signs of terminal manipulation, such as unexpected cursor movements or color changes during routine verification tasks. Implementing strict output encoding policies that treat all user-supplied data in metadata fields as untrusted and requiring explicit escaping before rendering is essential for preventing similar vulnerabilities in related applications. Regular audits of input validation logic across the application's information disclosure features are recommended to ensure no other vectors exist for terminal injection or visual spoofing attacks.