CVE-2026-118259 in opentelemetry-java
Summary
by MITRE • 10/28/2026
opentelemetry-java is the Java implementation of the OpenTelemetry API for recording telemetry, and SDK for managing telemetry recorded by the API. Prior to 1.67.0, W3CTraceContextPropagator.extract() uses regex delimiter processing that can exhibit quadratic backtracking while parsing tracestate headers containing long runs of spaces or tabs without a following comma. An unauthenticated attacker whose headers reach extraction can repeatedly block request or event-loop threads and cause excessive CPU consumption, with practical impact bounded by ingress header-size limits, proxy configuration, and threading. This issue is fixed in version 1.67.0.
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Analysis
by VulDB Data Team • 10/28/2026
The OpenTelemetry Java library serves as a critical component for distributed tracing and telemetry data collection within modern microservices architectures. It provides the Application Programming Interface (API) for recording metrics, traces, and logs, alongside an Software Development Kit (SDK) that manages the lifecycle of this recorded data. A significant security vulnerability was identified in versions prior to 1.67.0 concerning the W3CTraceContextPropagator class, specifically within its extract method responsible for parsing incoming trace context headers from HTTP requests or other transport mechanisms. This component is essential for correlating distributed traces across service boundaries by interpreting standardized header formats defined by the W3C Trace Context specification.
The core technical flaw lies in the implementation of regex delimiter processing used to parse the tracestate header field. The regular expression employed contains a pattern that allows for ambiguous matching when encountering long sequences of whitespace characters, such as spaces or tabs, particularly when these are not immediately followed by a comma separator. This structural ambiguity triggers catastrophic backtracking within the Java Regular Expression engine. When an attacker supplies a crafted tracestate header containing extensive runs of whitespace without proper delimiters, the regex engine attempts numerous alternative matching paths before failing to find a valid match. This results in exponential time complexity relative to the length of the input string, leading to severe performance degradation.
From an operational perspective, this vulnerability enables a Denial of Service attack against services that process telemetry data or rely on distributed tracing headers for request routing and context propagation. An unauthenticated attacker can exploit this by sending specially crafted HTTP requests with maliciously formatted tracestate headers. The resulting CPU consumption can block not only the specific thread handling the incoming request but also potentially exhaust event-loop threads in reactive frameworks like Netty, which are commonly used alongside OpenTelemetry for high-performance network I/O. This blocking effect effectively halts service availability and degrades overall system responsiveness. However, the practical impact is often bounded by ingress header size limits imposed by load balancers or reverse proxies, as well as specific threading models configured within the application server.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-400: Uncontrolled Resource Consumption, specifically manifesting as a Regular Expression Denial of Service (ReDoS). In terms of offensive security frameworks, this exploit technique corresponds to MITRE ATT&CK tactic T1496: Resource Hijacking, where an attacker consumes computational resources to disrupt service availability. The attack vector is classified under Network Access with no authentication required, leveraging the HTTP protocol as the delivery mechanism for the malicious payload embedded in standard headers that are typically trusted and processed automatically by telemetry instrumentation libraries.
Mitigation strategies primarily involve upgrading the OpenTelemetry Java library to version 1.67.0 or later, where this regular expression has been optimized to prevent catastrophic backtracking through improved pattern design or alternative parsing logic. For environments unable to immediately upgrade, defensive measures include configuring ingress controllers and API gateways to enforce strict limits on header sizes and lengths, thereby preventing the transmission of excessively long tracestate headers that could trigger the vulnerability. Additionally, implementing input validation rules that reject headers containing excessive consecutive whitespace characters can provide an additional layer of defense against this specific exploitation technique until a full patch deployment is achieved across all affected services.