CVE-2025-47934 is a high-severity vulnerability in OpenPGP.js, a widely used JavaScript implementation of the OpenPGP protocol, which is employed for encrypting, decrypting, signing, and verifying messages. The flaw exists in versions starting from 5.0.1 up to but not including 5.11.3, and from 6.0.0-alpha.0 up to but not including 6.1.1. The vulnerability arises from improper verification of cryptographic signatures (CWE-347) in the functions openpgp.verify and openpgp.decrypt when handling inline (non-detached) signed messages or signed-and-encrypted messages. Specifically, these functions can return a valid signature verification result while returning data that was not actually signed. This means an attacker who has access to a single valid signature and the corresponding plaintext can craft a malicious message that appears to be legitimately signed, but contains arbitrary data chosen by the attacker. Detached signature verification is not affected, as it does not return signed data. The attack exploits the fact that the verification functions do not ensure the returned data matches the originally signed content, allowing signature spoofing. This undermines the integrity guarantees of OpenPGP.js for inline-signed and signed+encrypted messages. The vulnerability does not require any privileges or user interaction and can be exploited remotely by anyone who can supply crafted messages. The issue has been patched in versions 5.11.3 and 6.1.1. Workarounds involve manually separating the message and signature using openpgp.readMessage and verifying signatures as detached by creating new messages with openpgp.createMessage and then verifying them separately. For decrypting and verifying signed+encrypted messages, a two-step process is recommended: first decrypt without verification keys, then verify signatures separately on the decrypted data. This vulnerability has a CVSS 4.0 score of 8.7 (high severity), reflecting its network attack vector, no required privileges or user interaction, and high impact on integrity. No known exploits are reported in the wild yet.

For European organizations, this vulnerability poses a significant risk to the integrity of communications secured using OpenPGP.js, especially in environments relying on inline signatures or combined signed-and-encrypted messages. Attackers can spoof signatures to make malicious messages appear authentic, potentially leading to misinformation, unauthorized command execution, or fraudulent transactions. This undermines trust in secure messaging, code signing, or document verification workflows that use OpenPGP.js. Sectors such as government, finance, legal, and critical infrastructure that rely on cryptographic assurances for secure communications and data integrity are particularly at risk. The vulnerability could facilitate phishing, social engineering, or supply chain attacks by allowing attackers to forge apparently valid signed messages without needing to compromise private keys. Since OpenPGP.js is a JavaScript library, web applications and browser-based tools using it for encryption and signature verification are vulnerable, increasing the attack surface in cloud services and SaaS platforms. The lack of requirement for authentication or user interaction means attacks can be automated and launched at scale. The impact on confidentiality is limited since the vulnerability affects signature verification rather than encryption itself, but the integrity and authenticity of messages are severely compromised. This can lead to loss of trust, regulatory compliance issues under GDPR and other data protection laws, and potential financial and reputational damage.

European organizations should urgently upgrade OpenPGP.js to versions 5.11.3 or 6.1.1 or later to apply the official patch. Until upgrades are possible, implement the recommended workarounds: for inline-signed messages, extract the message and signature(s) using openpgp.readMessage, then verify signatures as detached by creating new messages with openpgp.createMessage and passing them to openpgp.verify. For signed+encrypted messages, perform decryption without verification keys first, then verify the signatures separately on the decrypted data. Review all applications and services using OpenPGP.js to identify affected versions and usage patterns. Conduct code audits to ensure no inline signature verification is performed without these mitigations. Enhance monitoring for suspicious message patterns or signature verification anomalies. Educate developers and security teams about the vulnerability and the importance of proper signature verification. Consider additional layers of message integrity validation, such as out-of-band signature confirmation or multi-factor verification for critical transactions. Finally, maintain an inventory of cryptographic libraries and enforce strict update policies to reduce exposure to similar vulnerabilities.