Overview
A critical vulnerability, identified as CVE-2025-2516, has been found in WPS Office for Windows by Kingsoft. The flaw stems from the use of a weak cryptographic key pair in the software’s signature verification process, which may allow attackers to sign malicious components as legitimate. This issue is further compounded by older WPS Office versions failing to validate the update server’s certificate, making it vulnerable to Adversary-In-The-Middle (AITM) attacks.
Technical Details
This vulnerability involves inadequate encryption strength, formally classified as CWE-326. The weak cryptographic key used for signature verification could be recovered through brute-force techniques. Once the private key is obtained, an attacker can generate valid-looking signed components and inject them into the software update mechanism.
Older versions of WPS Office exacerbated this risk by not verifying the identity of the update server. This allowed attackers in a man-in-the-middle position to redirect users to malicious updates, fully compromising affected systems.
CVSS and Severity
Using the CVSS v4.0 scoring system, the vulnerability has been rated as Critical with a base score of 9.5. The vector string is:
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/U:Amber
This reflects:
- Attack is network-based
- No privileges or user interaction required
- High impact on confidentiality, integrity, and availability
- High complexity due to key recovery requirement
Attack Patterns
The vulnerability aligns with several attack patterns:
- CAPEC-20: Encryption Brute Forcing
- CAPEC-485: Signature Spoofing by Key Recreation
- CAPEC-187: Malicious Automated Software Update via Redirection
Real-World Exploitation
This vulnerability has already been weaponized by a threat actor, underlining its severity and the urgency for remediation.
Mitigation
Users are advised to update WPS Office to the latest secure version and ensure that update processes validate server certificates. Organizations should also monitor for signs of tampered updates and verify the authenticity of software components.
Further Information
More insights are available in the detailed research by ESET: WeLiveSecurity Report.
Conclusion
CVE-2025-2516 is a reminder of the critical role cryptographic strength and secure update channels play in software integrity. Organizations should treat this vulnerability as high priority and respond accordingly to prevent potential exploitation.