CVE-2026-81680 in openssl_encrypt
Summary
by MITRE • 08/27/2026
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.
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Analysis
by VulDB Data Team • 08/27/2026
The vulnerability identified in openssl_encrypt versions prior to 1.4.9 represents a critical failure in data integrity verification within envelope-format encrypted files. This flaw specifically pertains to the handling of recovery slots, which are specialized metadata structures designed to provide alternative decryption paths or backup mechanisms for file owners who may lose primary access credentials. The core technical deficiency lies in the authentication mechanism used during the decryption process. While the system correctly authenticates the payload data itself, it fails to verify the integrity and presence of these specific recovery-slot fields within the envelope structure. This omission creates a scenario where the cryptographic signature or message authentication code does not encompass the metadata governing recovery mechanisms, leaving them exposed to tampering without triggering an error condition that would indicate unauthorized modification.
From an operational perspective, this vulnerability allows attackers with access to encrypted files to silently strip out these recovery paths. By modifying the file header and removing the fields associated with recovery slots, an attacker can effectively disable any backup decryption methods or emergency access provisions established by the data owner. This action does not require re-encrypting the payload because the authentication check passes for the remaining valid components of the envelope format. Consequently, if a legitimate user loses their primary key or encounters issues accessing the file through standard means, they will find that no alternative recovery options exist. The attacker achieves this by simply editing the header structure to delete the relevant sections, exploiting the lack of cryptographic binding between the payload authentication and the metadata integrity checks.
This type of vulnerability aligns with CWE-354, which describes improper validation of integrity check values, specifically when the validation does not cover all necessary components of a message or file structure. Furthermore, it relates to CWE-16, where configuration errors allow for unauthorized modification of critical system settings or data structures. In terms of offensive security frameworks such as MITRE ATT&CK, this behavior is consistent with techniques involving Data Obfuscation and Defense Evasion, particularly the manipulation of file attributes or metadata to hinder incident response and recovery efforts. The ability to remove recovery mechanisms without detection significantly increases the impact of a compromise by ensuring that once access is denied through legitimate channels, restoration becomes impossible unless backups from before the tampering occurred are available.
Mitigating this vulnerability requires an immediate upgrade to openssl_encrypt version 1.4.9 or later, where the authentication scope has been expanded to include recovery-slot fields within the envelope format. Developers and system administrators should verify that their encryption implementations strictly adhere to updated specifications that ensure all metadata components contributing to access control are included in integrity checks. Additionally, organizations relying on these encrypted files for critical data retention should implement regular backup verification processes to detect any unauthorized modifications to file headers or recovery structures before they result in permanent loss of access. Ensuring that the cryptographic envelope format enforces end-to-end authentication across both payload and metadata is essential to maintaining the confidentiality and availability guarantees provided by encryption systems.