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open-telemetry/opentelemetry-go · Security

opentelemetry-go: OTLP HTTP exporters read unbounded HTTP response bodies

GHSA ID
GHSA-w8rr-5gcm-pp58
CVE ID
CVE-2026-39882
Severity
medium
Published
Updated
CVSS
5.3 · CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS v3
5.3 · CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Description

overview: this report shows that the otlp HTTP exporters (traces/metrics/logs) read the full HTTP response body into an in-memory bytes.Buffer without a size cap.

this is exploitable for memory exhaustion when the configured collector endpoint is attacker-controlled (or a network attacker can mitm the exporter connection).

severity

HIGH

not claiming: this is a remote dos against every default deployment. claiming: if the exporter sends traces to an untrusted collector endpoint (or over a network segment where mitm is realistic), that endpoint can crash the process via a large response body.

callsite (pinned):

  • exporters/otlp/otlptrace/otlptracehttp/client.go:199
  • exporters/otlp/otlptrace/otlptracehttp/client.go:230
  • exporters/otlp/otlpmetric/otlpmetrichttp/client.go:170
  • exporters/otlp/otlpmetric/otlpmetrichttp/client.go:201
  • exporters/otlp/otlplog/otlploghttp/client.go:190
  • exporters/otlp/otlplog/otlploghttp/client.go:221

permalinks (pinned):

root cause: each exporter client reads resp.Body using io.Copy(&respData, resp.Body) into a bytes.Buffer on both success and error paths, with no upper bound.

impact: a malicious collector can force large transient heap allocations during export (peak memory scales with attacker-chosen response size) and can potentially crash the instrumented process (oom).

affected component:

  • go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp
  • go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp
  • go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp

repro (local-only):

unzip poc.zip -d poc
cd poc
make canonical resp_bytes=33554432 chunk_delay_ms=0

expected output contains:

[CALLSITE_HIT]: otlptracehttp.UploadTraces::io.Copy(resp.Body)
[PROOF_MARKER]: resp_bytes=33554432 peak_alloc_bytes=118050512

control (same env, patched target):

unzip poc.zip -d poc
cd poc
make control resp_bytes=33554432 chunk_delay_ms=0

expected control output contains:

[CALLSITE_HIT]: otlptracehttp.UploadTraces::io.Copy(resp.Body)
[NC_MARKER]: resp_bytes=33554432 peak_alloc_bytes=512232

attachments: poc.zip (attached)

PR_DESCRIPTION.md

attack_scenario.md

poc.zip

Fixed in: https://github.com/open-telemetry/opentelemetry-go/pull/8108

CWEs

  • CWE-789 · Memory Allocation with Excessive Size Value

References

Open GitHub