CVE-2026-81691 in openssl_encrypt
Summary
by MITRE • 08/27/2026
openssl_encrypt versions before 1.4.9 fail to validate server URLs in login and register_with_email functions, accepting unencrypted http:// URLs and unconfigured hosts. Attackers on the network path can intercept cleartext credentials including client_id, passwords, and JWTs to achieve full keyserver account takeover.
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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 transport layer security validation within the authentication mechanisms of the application. Specifically, the login and register_with_email functions exhibit insufficient input validation regarding server URLs. This flaw allows the system to accept and process unencrypted HTTP connections instead of enforcing secure HTTPS protocols. By failing to validate that the connection is encrypted, the software inadvertently exposes sensitive communication channels to passive network interception attacks.
From a technical perspective, this issue stems from a lack of strict protocol enforcement in the client-side or server-side logic responsible for establishing sessions during user registration and authentication. When an attacker positions themselves on the same network path as the victim, such as through a compromised Wi-Fi access point or via man-in-the-middle techniques, they can intercept all data transmitted over these unencrypted HTTP connections. The absence of TLS encryption means that sensitive credentials are transmitted in cleartext, making them trivially readable by any entity with packet capture capabilities on the network segment.
The operational impact of this vulnerability is severe and directly leads to full account takeover. Because client identifiers, user passwords, and JSON Web Tokens (JWTs) are exposed during transmission, attackers can harvest these credentials without needing to exploit complex application logic flaws or bypass multi-factor authentication mechanisms that might otherwise protect the accounts. Once an attacker obtains a valid JWT or password hash from the intercepted traffic, they can authenticate as the victim on any device, effectively gaining complete control over the keyserver account and potentially accessing associated cryptographic keys or sensitive data stored within the platform.
This vulnerability aligns with CWE-319, which classifies cleartext transmission of sensitive information, a common weakness in applications that do not enforce secure communication channels for authentication flows. Furthermore, from an adversary perspective, this behavior facilitates MITM attacks as described in the ATT&CK framework under techniques such as Network Sniffing and Credential Access. The exploitation does not require sophisticated tooling beyond standard packet analysis software, making it a high-risk vulnerability accessible to low-skilled attackers operating on shared or untrusted networks.
To mitigate this risk, immediate updates to openssl_encrypt versions 1.4.9 or later are required if such an update is available and addresses the URL validation logic. In cases where version upgrades are not immediately feasible, organizations must implement strict network-level controls to enforce HTTPS usage across all endpoints involved in authentication processes. This includes configuring web servers to redirect HTTP traffic to HTTPS and ensuring that client applications reject non-secure connections at the code level by validating certificate chains and enforcing TLS 1.2 or higher protocols. Additionally, implementing Content Security Policy headers with strict transport security directives can help prevent browsers from loading resources over insecure channels, thereby reducing the attack surface for credential interception attacks.