CVE-2026-81872: OpenTelemetry-Go: BatchProcessor can busy-spin when export buffer is full
Summary
A BatchingProcessor in go.opentelemetry.io/otel/sdk/log can enter a tight CPU loop when the asynchronous export buffer is full. Under exporter backpressure, attacker-driven high-volume log emission can keep the queue at or above the batch size, causing repeated immediate export retries and a denial of service through CPU exhaustion.
Introduced in commit: 4af9c20
Details
NewBatchingProcessor wraps the exporter with newBufferExporter(exporter, 1) (sdk/log/batch.go:116-122), so the asynchronous export input can fill quickly when the downstream exporter blocks. The poll goroutine dequeues a batch with b.q.TryDequeue, calls b.exporter.EnqueueExport(r), and then immediately sends on b.pollTrigger whenever qLen >= b.batchSize (sdk/log/batch.go:129-165).
bufferExporter.EnqueueExport is non-blocking: it sends to e.input if possible and returns false in the default case when the channel is full (sdk/log/exporter.go:221-248). TryDequeue leaves q.len unchanged when the write callback returns false (sdk/log/batch.go:289-314). Therefore, while the exporter is backpressured, EnqueueExport fails, the queue remains at or above one full batch, and the poll loop continuously retriggers itself without waiting for the ticker.
PoC
validation-artifact.zip
The validation artifact contains a PoC bundle:
- validation-artifact.tar:main.go: PoC source. - validation-artifact.tar:README.md: build/run notes. - validation-artifact.tar:buildfailed.log: captured build failure from the validation environment.
The PoC configures a blocking exporter and a BatchingProcessor with WithExportMaxBatchSize(1), WithExportInterval(5time.Second), and WithMaxQueueSize(2048). It emits 1000 records, records a CPU profile for 750 ms while the exporter is blocked, then writes /workspace/validationartifacts/busyloop.pprof.
Reproduction steps from an affected checkout at commit 4af9c20:
sh cd /workspace/opentelemetry-go git checkout 4af9c20
mkdir -p validationpoc/busyloop /workspace/validationartifacts /tmp/batchingprocessor-busyloop-poc tar -xf /path/to/this/finding/validation-artifact.tar -C /tmp/batchingprocessor-busyloop-poc cp /tmp/batchingprocessor-busyloop-poc/main.go validationpoc/busyloop/main.go
go build -o validationpoc/busyloop/busyloop ./validationpoc/busyloop ./validationpoc/busyloop/busyloop go tool pprof -top /workspace/validationartifacts/busyloop.pprof
Expected program output:
text cpu profile written to /workspace/validationartifacts/busyloop.pprof
Expected profile evidence: hot functions should include (BatchingProcessor).poll, (queue).TryDequeue, and (bufferExporter).EnqueueExport, showing repeated export attempts while the exporter is blocked.
Impact
This is an availability vulnerability: uncontrolled CPU consumption caused by a busy-spin retry loop. Applications using sdk/log BatchingProcessor are impacted when an attacker can cause sustained log emission and the configured exporter or downstream collector is slow, blocked, or otherwise backpressured. The impact is limited to the embedding process but can degrade or deny service for that application.
Other sources
OpenTelemetry-Go is the Go implementation of OpenTelemetry. Prior to version 0.21.0, the go.opentelemetry.io/otel/sdk/log BatchingProcessor can enter a tight CPU loop when attacker-driven log emission fills its asynchronous export buffer while the exporter is backpressured. NewBatchingProcessor wraps the exporter with newBufferExporter(exporter, 1), and the poll loop calls queue.TryDequeue and bufferExporter.EnqueueExport before immediately signaling pollTrigger whenever the queue remains at or above batchSize. Because a failed nonblocking EnqueueExport leaves the queue length unchanged, the processor repeatedly retries without waiting for its ticker, exhausting CPU and degrading or denying service in the embedding process. This issue is fixed in version 0.21.0.
— MITRE
OpenTelemetry-Go: BatchProcessor can busy-spin when export buffer is full
— Microsoft
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/go.opentelemetry.io/otel/sdk/logto a version that resolves this vulnerability.Fixed in 0.21.0 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 1.7.0-1 - Upgrade
Upgrade
go.opentelemetry.io/otel/sdk/logto a version that resolves this vulnerability.Fixed in 0.21.0
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Deployments using go.opentelemetry.io/otel/sdk/log BatchingProcessor before version 0.21.0 are affected when their asynchronous export buffer becomes full while the exporter is backpressured. The impact occurs in the embedding Go process, where CPU exhaustion can degrade or deny service.
What conditions are required for exploitation?
An attacker must be able to drive sufficient log emission to keep the processor queue at or above its batch size. The exporter must also be backpressured so that its single-entry asynchronous export buffer cannot accept another export.
Is the default processor construction affected?
Yes. NewBatchingProcessor wraps the exporter with newBufferExporter(exporter, 1), creating a buffer with capacity one. When that buffer is full, a failed nonblocking enqueue can leave the queue unchanged and trigger repeated immediate retries.
How can I determine whether this is occurring?
Look for sustained high CPU consumption in a process using the affected BatchingProcessor during periods of high log volume and exporter backpressure. The processor may repeatedly retry exports without waiting for its ticker while its queue remains at or above batchSize.
What is the available fix?
Upgrade OpenTelemetry-Go to version 0.21.0, which fixes the issue.