OpenTelemetry Operator for Kubernetes's ServiceMonitor bearerTokenFile reads arbitrary local file and sends contents as bearer authGHSA-cxh2-4639-vmc5
HIGHFix: open-telemetry/opentelemetry-operator#5104GHSA-cxh2-4639-vmc5 is a high-severity (CVSS 7.7) Information Exposure vulnerability in github.com/open-telemetry/opentelemetry-operator. A fix is available for github.com/open-telemetry/opentelemetry-operator — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-cxh2-4639-vmc5.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-cxh2-4639-vmc5 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
github.com/open-telemetry/opentelemetry-operatorReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Affected
Repository: github.com/open-telemetry/opentelemetry-operator Component: cmd/otel-allocator (TargetAllocator) Companion: Prometheus Operator API types (CRDs)
Summary
OpenTelemetry Operator's TargetAllocator watches ServiceMonitor resources via the Prometheus Operator CR watcher and converts each selected endpoint into a Prometheus scrape configuration entry. The endpoint field bearerTokenFile is preserved through the conversion as HTTPClientConfig.Authorization.CredentialsFile. The OpenTelemetry Collector, configured with the Prometheus receiver, then loads that scrape config and, at scrape time, reads the file from its own pod filesystem and sends the contents as Authorization: Bearer ... to the scrape endpoint.
A tenant who can create or update a ServiceMonitor selected by TargetAllocator can set bearerTokenFile: /var/run/secrets/kubernetes.io/serviceaccount/token and a scrape target the tenant controls. The Collector then ships its mounted service account JWT to that target on every scrape interval.
The Prometheus Operator project addressed the same primitive via the ArbitraryFSAccessThroughSMs.Deny admission/runtime guard.
Preconditions
The OpenTelemetry Collector needs to be deployed with targetAllocator.prometheusCR.enabled: true and serviceMonitorSelector / serviceMonitorNamespaceSelector matching at least one namespace where the attacker can create or update ServiceMonitor (or paired with a TargetAllocator resource with the same respective settings). The Collector pod needs to have its service account token mounted. The Collector needs to be able to reach the scrape target chosen by the attacker.
Impact
Tenant ServiceMonitor write becomes equivalent to the OpenTelemetry Collector pod's service account against the Kubernetes API. Real impact depends on what the Collector service account is granted in a given deployment. Typical cluster monitoring setups grant pod, node, endpoint, namespace, and service list across the cluster, which is enough to enumerate and identify further targets. The same primitive can read any file the Collector pod has on disk including mounted certificates and other tokens.
Fix
https://github.com/open-telemetry/opentelemetry-operator/pull/5104 adds support to disable service and podmonitor endpoints that read arbitrary files.
DenyFSAccessThroughSMs causes the Target Allocator to drop ServiceMonitor and PodMonitor endpoints that reference arbitrary files on the file system. When enabled, endpoints with bearerTokenFile, tlsConfig.caFile, tlsConfig.certFile, or tlsConfig.keyFile are dropped from the produced scrape configuration while the remaining endpoints are kept. This prevents tenants from stealing the Collector's service account token via ServiceMonitor bearerTokenFile references. This is the equivalent of ArbitraryFSAccessThroughSMs.Deny from the Prometheus Operator.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/open-telemetry/opentelemetry-operator | all versions | 0.152.0go get github.com/open-telemetry/opentelemetry-operator@v0.152.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/open-telemetry/opentelemetry-operator, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/open-telemetry/opentelemetry-operator to 0.152.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-cxh2-4639-vmc5 is resolved across your whole dependency graph.
Workarounds
Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
A flaw was found in the OpenTelemetry Operator for Kubernetes. The TargetAllocator preserves the ServiceMonitor bearerTokenFile field through to the Collector's Prometheus scrape configuration. A tenant who can create or update a ServiceMonitor can set bearerTokenFile to the Collector's mounted service account token…
Upgrade to opentelemetry-operator 0.152.0 or later, which adds DenyFSAccessThroughSMs support to drop ServiceMonitor and PodMonitor endpoints that reference arbitrary files on the file system.Source: Red Hat security advisory for GHSA-cxh2-4639-vmc5 (CC BY 4.0)
Frequently Asked Questions
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