Description

openssl_encrypt before 1.4.9 fails to sanitize the email field of imported identity documents, allowing attackers to inject ANSI escape sequences that forge the fingerprint verification line displayed to users. Attackers can deliver a crafted identity bundle through normal contact-exchange flows or keyserver responses to manipulate terminal output and display a fraudulent fingerprint, bypassing the out-of-band verification mechanism that protects against key substitution attacks.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-08-27T17:21:01.440Z",
  "pubdate": "2026-08-27T17:21:01.440Z",
  "executiveSummary": "The openssl_encrypt library, in versions prior to 1.4.9, contains a critical vulnerability regarding the improper sanitization of identity document metadata. Specifically, the email field within imported identity bundles fails to filter ANSI escape sequences.\nThis vulnerability allows an attacker to perform a terminal-based injection attack that enables the forgery of fingerprint verification lines displayed to end-users. By crafting a malicious identity bundle, an attacker can manipulate the terminal rendering engine to overwrite or hide legitimate cryptographic fingerprint data, effectively substituting it with a fraudulent visual representation.\nThe risk implication is severe, as it subverts the out-of-band verification process—a fundamental security control designed to detect man-in-the-middle key substitution attacks. Successful exploitation does not require prior authentication or elevated privileges, provided the attacker can initiate a contact-exchange flow or influence a keyserver response. By exploiting the inherent trust users place in terminal-based security displays, attackers can facilitate unauthorized identity impersonation, compromising the integrity of encrypted communications.\nMitigation requires an immediate update to the library, as the flaw resides within the parsing logic of user-supplied identity fields.",
  "technicalDetails": "The vulnerability originates from the lack of input validation and output sanitization within the `openssl_encrypt` identity document parser. Specifically, the component responsible for processing the email field of an imported identity document fails to restrict or strip control characters, specifically ANSI escape sequences (such as ESC [ or CSI codes).\nExploitation is achieved by embedding terminal control sequences within the email field of an identity bundle. When the application passes this data to the terminal emulator for display—typically during the fingerprint verification phase—the terminal interprets these sequences as commands rather than literal string data. An attacker can leverage these sequences to move the cursor, clear lines, or overwrite existing text on the terminal screen.\nThe attack flow follows these stages: 1) The attacker constructs a malicious identity object where the email attribute contains a payload of ANSI sequences designed to obfuscate the legitimate fingerprint and render a spoofed one. 2) The attacker distributes this bundle via standard contact-exchange protocols or via a malicious keyserver response. 3) The victim's client application processes the identity bundle and executes the terminal output routine to show the fingerprint. 4) The terminal emulator renders the fraudulent fingerprint displayed by the malicious sequences, while effectively masking the actual cryptographic fingerprint contained in the bundle.\nBecause the terminal emulator is instructed to display the forged string at the specific coordinate expected by the user for verification, the victim is presented with a falsified confirmation of authenticity. This bypasses the security intent of the verification process, as the user is led to believe they are verifying a legitimate key when they are actually interacting with a compromised or attacker-controlled identity.\nThe vulnerability affects all versions of `openssl_encrypt` prior to 1.4.9. The exposure is dependent on the application's implementation of terminal display logic, but remains inherent to the library's failure to sanitize the email field before returning the data to the calling application. Exploitation is remote and requires no specific interaction from the victim beyond the normal receipt or viewing of the identity bundle, making it highly effective against users relying on CLI-based verification tools."
}