Description

openssl_encrypt versions before 1.4.9 fail to authenticate recovery-slot presence in envelope-format encrypted files, allowing attackers to remove recovery slots without re-encrypting the payload. Attackers can modify the file header to delete recovery-slot fields and bypass authentication, silently removing recovery paths the owner deliberately added.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "4.0",
  "pubDate": "2026-08-27T17:20:57.300Z",
  "pubdate": "2026-08-27T17:20:57.300Z",
  "executiveSummary": "The openssl_encrypt utility, in versions prior to 1.4.9, contains a critical authentication vulnerability regarding the processing of envelope-format encrypted files.\nThe vulnerability allows an unauthenticated attacker to manipulate the file header to remove recovery-slot fields, effectively bypassing the integrity protections intended for recovery paths.\nBecause the system fails to authenticate the presence or integrity of these recovery slots, an attacker can silently excise them from an encrypted file without needing to decrypt, modify, or re-encrypt the underlying payload.\nThis represents a significant security risk to data availability and recovery assurance, as the owner's authorized recovery mechanisms can be removed by an adversary with access to the encrypted file.\nExploitation does not require elevated privileges or complex cryptographic attacks; it is achieved through direct manipulation of the file's structure. Consequently, the primary impact is the unauthorized destruction of data recovery paths, leading to potential permanent data loss if the primary access method fails.",
  "technicalDetails": "The root cause of this vulnerability lies in an insufficient authentication check within the openssl_encrypt implementation for envelope-format encrypted files. Specifically, the software fails to enforce strict integrity validation for the presence and content of recovery-slot metadata contained within the file header.\nIn the context of envelope encryption, recovery slots are designed to provide alternate paths for data access, usually via a master key or a secondary recovery key. The vulnerability exists because the parser responsible for reading the envelope header implicitly trusts the structure defined in the file header without verifying that the defined recovery slots remain unaltered from their original, legitimate state.\nAn attacker can exploit this by performing manual structural modifications to the file header. The attack flow is as follows: 1) The attacker obtains an encrypted file containing one or more valid recovery slots. 2) Using a binary editor or a script, the attacker parses the envelope structure to locate the recovery-slot field definitions. 3) The attacker modifies the header fields to remove or zero-out these entries, effectively updating the file's metadata while leaving the main encrypted payload intact. 4) Because the validation logic does not cryptographically authenticate the header's recovery-slot definitions, the modified file is accepted as legitimate by subsequent decryption or management processes.\nThis manipulation results in the silent removal of recovery paths. The payload itself remains secure against decryption by the attacker, but the legitimate owner loses the ability to utilize the recovery slots, which may be critical if the primary decryption credentials are lost. This vulnerability affects all versions of openssl_encrypt prior to 1.4.9. The exposure is local to the file system or wherever the encrypted files are stored, and no network interaction is strictly required for the modification itself, though the files may be delivered via network protocols.\nThe post-exploitation impact is focused on denial-of-service against the data owner's recovery capabilities. By removing these slots, an attacker can ensure that if the primary encryption key is compromised or lost, the owner has no fall-back mechanism, rendering the data inaccessible."
}