CVE-2026-118259

opentelemetry-java: Quadratic CPU consumption in W3C tracestate parsing

OpenTelemetry Java's W3C trace-context propagator permits excessive CPU consumption when extracting crafted tracestate headers, potentially leading to denial of service. Regex backtracking causes quadratic parsing time for headers containing long runs of spaces or tabs without a following comma.

Workarounds

If upgrading is not possible, reject or remove oversized tracestate headers before trace-context extraction. This reduces the per-request parsing cost but does not eliminate the risk from repeated requests.

An unauthenticated attacker whose headers reach W3CTraceContextPropagator.extract() can cause excessive CPU usage through crafted requests. Parsing blocks the calling thread, potentially affecting other connections when extraction runs on a shared event-loop thread. Actual impact depends on ingress header-size limits, proxy configuration, and threading. Header-size limits reduce the per-request cost but do not eliminate the vulnerability.

A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use. Typical impact: denial of service when input is crafted to trigger backtracking.

CVE-2026-118259 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.67.0); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

Upgrade io.opentelemetry:opentelemetry-api to version 1.67.0 or later. PR #8914 replaces regex delimiter splitting with literal comma scanning and explicit whitespace trimming.

1. What is CVE-2026-118259? CVE-2026-118259 is a medium-severity inefficient regular expression (ReDoS) vulnerability in io.opentelemetry:opentelemetry-api (maven), affecting versions <= 1.66.0. It is fixed in 1.67.0. A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use.
2. How severe is CVE-2026-118259? CVE-2026-118259 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of io.opentelemetry:opentelemetry-api are affected by CVE-2026-118259? io.opentelemetry:opentelemetry-api (maven) versions <= 1.66.0 is affected.
4. Is there a fix for CVE-2026-118259? Yes. CVE-2026-118259 is fixed in 1.67.0. Upgrade to this version or later.
5. Is CVE-2026-118259 exploitable, and should I be worried? Whether CVE-2026-118259 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-118259 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-118259? Upgrade io.opentelemetry:opentelemetry-api to 1.67.0 or later.

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