Description

openssl_encrypt versions before 1.4.0 use Python's non-cryptographic random module for steganographic pixel selection in the generate_pseudorandom_sequence function. Attackers who know the password can recover the Mersenne Twister state from approximately 624 outputs and predict pixel locations containing hidden data for extraction.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.5",
  "pubDate": "2026-08-17T11:16:41.813Z",
  "pubdate": "2026-08-17T11:16:41.813Z",
  "executiveSummary": "A critical vulnerability exists in openssl_encrypt versions before 1.4.0, specifically involving the use of insecure cryptographic practices for steganographic data concealment. The flaw resides in the generate_pseudorandom_sequence function, which improperly utilizes Python's non-cryptographic random module instead of a cryptographically secure pseudo-random number generator (CSPRNG). This implementation failure allows an attacker who knows the password to compromise the underlying Mersenne Twister state.\nThe primary impact of this vulnerability is the complete compromise of data confidentiality within steganographically processed media. By observing approximately 624 outputs generated by the flawed function, an unauthorized actor can successfully predict the exact pixel locations utilized for hidden data insertion and extraction. This exposes sensitive information embedded within the pixel matrix to unauthorized retrieval.\nThe affected product is openssl_encrypt across all versions preceding 1.4.0. Exploitation of this vulnerability requires the attacker to possess prior knowledge of the password used in the encryption process, alongside the ability to analyze a sufficient sequence of outputs to reconstruct the internal state of the generator. The risk implication is significant for applications relying on this library for covert data transmission, as the deterministic nature of the random module completely undermines the security guarantees of the steganographic mechanism.",
  "technicalDetails": "The root cause of the vulnerability is the improper selection of a pseudo-random number generator within the generate_pseudorandom_sequence function of openssl_encrypt versions before 1.4.0. Rather than employing a CSPRNG designed to resist state prediction and cryptographic analysis, the developers utilized Python's standard random module, which implements the Mersenne Twister algorithm (specifically MT19937). The Mersenne Twister is entirely deterministic and unsuitable for security-sensitive applications because observing a sequential series of its outputs exposes its internal state.\nThe vulnerable component is explicitly the generate_pseudorandom_sequence function responsible for pixel selection during the steganographic embedding and extraction processes. In these affected versions, the sequence of pixels chosen to contain hidden payload data is directly determined by the output of the predictable random module. Because the underlying state transitions are mathematically reversible and predictable, the security posture of the application is severely degraded.\nThe attack flow proceeds as follows: First, an attacker interacts with the system or intercepts steganographically altered media produced by the vulnerable openssl_encrypt function. Second, leveraging knowledge of the password, the attacker obtains approximately 624 sequential outputs generated by the vulnerable function. Third, the attacker feeds these observed outputs into state-recovery algorithms designed for the Mersenne Twister algorithm, thereby reconstructing the internal 33024-bit state of the generator. Fourth, once the internal state is successfully cloned or recovered, the attacker can accurately compute all past and future pseudo-random values produced by that instance. Finally, the attacker applies this predictive capability to determine the exact pixel locations containing hidden data, enabling unauthorized extraction and decryption of the payload without further interaction.\nRegarding operational conditions, authentication requirements and specific network exposure vectors are dependent on the broader application architecture implementing openssl_encrypt, but the cryptographic weakness itself is inherent to the function's internal logic. The payload behavior involves deterministic pixel indexing for steganographic embedding, which facilitates passive or active post-exploitation extraction of covert data streams by any adversary capable of state reconstruction."
}