CVE-2026-39882

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):

• https://github.com/open-telemetry/opentelemetry-go/blob/248da958375e4dfb4a1105645107be3ef04b1c59/exporters/otlp/otlptrace/otlptracehttp/client.go#L199
• https://github.com/open-telemetry/opentelemetry-go/blob/248da958375e4dfb4a1105645107be3ef04b1c59/exporters/otlp/otlptrace/otlptracehttp/client.go#L230
• https://github.com/open-telemetry/opentelemetry-go/blob/248da958375e4dfb4a1105645107be3ef04b1c59/exporters/otlp/otlpmetric/otlpmetrichttp/client.go#L170
• https://github.com/open-telemetry/opentelemetry-go/blob/248da958375e4dfb4a1105645107be3ef04b1c59/exporters/otlp/otlpmetric/otlpmetrichttp/client.go#L201
• https://github.com/open-telemetry/opentelemetry-go/blob/248da958375e4dfb4a1105645107be3ef04b1c59/exporters/otlp/otlplog/otlploghttp/client.go#L190
• https://github.com/open-telemetry/opentelemetry-go/blob/248da958375e4dfb4a1105645107be3ef04b1c59/exporters/otlp/otlplog/otlploghttp/client.go#L221

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

CVE-2026-39882 has a CVSS score of 5.3 (Medium). The vector is reachable from an adjacent network, 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 (1.43.0, 0.19.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-39882? CVE-2026-39882 is a medium-severity security vulnerability in go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp (go), affecting versions < 1.43.0. It is fixed in 1.43.0, 0.19.0.
2. How severe is CVE-2026-39882? CVE-2026-39882 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 packages are affected by CVE-2026-39882?
   • go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp (go) (versions < 1.43.0)
   • go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp (go) (versions < 1.43.0)
   • go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp (go) (versions < 0.19.0)
4. Is there a fix for CVE-2026-39882? Yes. CVE-2026-39882 is fixed in 1.43.0, 0.19.0. Upgrade to this version or later.
5. Is CVE-2026-39882 exploitable, and should I be worried? Whether CVE-2026-39882 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-2026-39882 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-2026-39882?
   • Upgrade go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp to 1.43.0 or later
   • Upgrade go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp to 1.43.0 or later
   • Upgrade go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp to 0.19.0 or later