A critical WSO2 vulnerability patched earlier this year is now being exploited in the wild by threat actors seeking access to sensitive enterprise data.
WSO2 is an open source middleware platform that enables organizations to design, secure, integrate, and manage APIs, services, and identities across hybrid and multi-cloud environments.
The platform has nearly 1,000 enterprise customers worldwide in sectors such as banking, government, telecom, and logistics. Thousands more have adopted it through open source deployments, OEMs, and partners.
Exposure management firm WatchTowr warned on Tuesday that a vulnerability tracked as CVE-2026-5430, which WSO2 patched in April, is being exploited in malicious attacks.
The flaw carries a maximum CVSS score of 10. According to a vendor advisory issued in May, it can let attackers bypass authentication and take over accounts.
“JWT authentication can be bypassed when a token is signed using an unsupported algorithm, allowing unauthorized access,” WSO2 explained, adding, “Successful exploitation of the vulnerability may lead to unauthorized access, including potential compromise of administrative accounts and full account takeover.”
The API Manager, API Control Plane, Traffic Manager, and Universal Gateway products are affected.
Yordan Ganchev, principal threat intelligence specialist at WatchTowr, told SecurityWeek that the company’s honeypot network saw the first exploitation attempt on September 13.
Ganchev explained that the attacker used a forged JWT token, which allowed WatchTowr researchers to determine the attacker’s goal.
“The forged token yields access to every API backend endpoint and its credentials, consumer keys and secrets for every registered application,” Ganchev said. “The service is also by definition made to intercept API requests on their way to internal systems, which provides a great opportunity to tap and steal sensitive data in transit and interact with internal services through this ‘Lateral Movement-as-a-Service’ product.”
Ganchev added, “We observed a single attacker targeting the wrong product, but when we replayed their payload on the real one, it worked. Our honeypots were fortunate to be mixed up, but the same may not be guaranteed about real victim systems.”
The expert also noted that the CVE record for CVE-2026-5430 was published only in early August, and technical details still do not appear to be public. However, WatchTowr easily reproduced the vulnerability based on the vendor’s patch.
“The only mystery here is what took everyone else so long,” Ganchev said.
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