CVE-2026-85473 in java-jwt
Summary
by MITRE • 10/14/2026
The auth0/java-jwt library may terminate a thread if it receives a JWT with a timestamp claim (exp, nbf, iat) containing an out-of-range value. The condition occurs during token parsing, prior to signature verification. Repeated requests of this nature may lead to degraded availability of the affected service.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability in the auth0/java-jwt library represents a significant reliability risk due to improper handling of malformed JSON Web Tokens (JWTs). Specifically, when the library processes an incoming JWT that contains timestamp claims such as expiration time (exp), not before (nbf), or issued at (iat) with values outside the expected range, it triggers an unhandled exception condition. This flaw occurs during the initial parsing phase of token validation, which precedes the critical signature verification step. Because the library does not gracefully handle these out-of-range numeric values, it causes the underlying Java thread to terminate abruptly rather than returning a standard error code or rejecting the token with a proper HTTP response.
From an operational perspective, this behavior creates a direct path for Denial of Service (DoS) attacks against any service relying on this library for authentication and authorization. An attacker can craft malicious JWTs containing extreme timestamp values that trigger the thread termination logic. By sending repeated requests with these malformed tokens, an adversary can systematically exhaust available server threads or worker processes. Since each request consumes a thread that is then killed rather than recycled, the application's capacity to handle legitimate traffic degrades rapidly. This leads to service unavailability for genuine users, effectively achieving a denial of service without needing to exploit complex logic flaws or consume excessive computational resources in traditional ways.
This vulnerability aligns with CWE-20: Improper Input Validation and CWE-755: Improper Handling of Exceptional Conditions. The failure to validate the range of timestamp fields before processing constitutes an input validation error, while the resulting thread termination reflects a poor exception handling strategy that fails to maintain system stability under adverse conditions. In terms of offensive security frameworks, this flaw facilitates attacks categorized under MITRE ATT&CK technique T1498: Network Denial of Service, specifically through resource exhaustion via application-level logic flaws rather than network-layer flooding.
To mitigate this risk, developers must upgrade the auth0/java-jwt library to a patched version that implements robust input validation for all JWT claims before processing begins. The fix should ensure that timestamp values are checked against reasonable bounds and that any out-of-range data results in a controlled rejection of the token with an appropriate error response, rather than throwing unhandled exceptions that crash threads. Additionally, implementing rate limiting on authentication endpoints can help mitigate the impact of such attacks by throttling requests from sources exhibiting suspicious patterns of malformed JWT submissions. Monitoring application logs for frequent thread termination events or exception stack traces related to JWT parsing can also aid in early detection and response to potential exploitation attempts.