A critical security vulnerability has been found in OpenPGP.js, a widely used JavaScript cryptography library that enables secure encrypted communications and digital signature verification in web-based applications.
This flaw, designated as CVE-2025-47934, exposed users to the risk of digital signature spoofing, potentially undermining the foundation of trust upon which encrypted communications and document signing are based.
OpenPGP.js is relied upon by a wide array of encrypted email services and secure messaging platforms, making this vulnerability especially significant for the global web security ecosystem.
Technical Details: How Attackers Exploited Packet Parsing
At the core of the vulnerability is the way OpenPGP.js parsed and validated signed messages in compliance with the OpenPGP protocol.
OpenPGP messages are structured as ordered binary packets.
A typical signed message contains a sequence that starts with a One-Pass Signature packet, followed by the Literal Data packet containing the signed content, and finally a Signature packet which cryptographically authenticates the data.
The intention is that the signature is always tied uniquely to the specific content. However, the researchers at Codean Labs discovered that the library did not sufficiently enforce strict grammar validation when parsing these packets.
The flaw could be triggered by appending a malicious Compressed Data packet to an otherwise legitimate signed message.
This extra packet could encapsulate arbitrary attacker-crafted content.
During normal usage, when an application verifies a signature using OpenPGP.js, the function first checks the signature against the correct, original data and gives the expected pass/fail result.
Severity, Response, And Best Practices
The practical impact of this vulnerability is considerable, especially given the importance of digital signature verification for secure software development, document validation, and end-to-end encrypted communication.
Attackers exploiting this flaw could carry out phishing, document forgery, or introduce arbitrary malicious code into systems that rely on OpenPGP.js for trust.
Any application or service that directly exposes the message data returned by OpenPGP.js after signature verification was potentially at risk.
According to the Report, Security researchers responsibly disclosed the flaw to the maintainers of OpenPGP.js, who reacted promptly by preparing and releasing patched versions. The vulnerability has been fully fixed in OpenPGP.js versions 5.11.3 and 6.1.1.
The fix involved enforcing strict grammar compliance during message parsing, ensuring that only correctly structured and fully signed packets are processed and accepted by the library.
Users and developers are strongly advised to upgrade to the latest versions immediately.
If you use applications or extensions such as encrypted email clients that rely on OpenPGP.js for cryptographic operations, it is vital to ensure that your software is updated to include the patched library.
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