OpenTelemetry-Go: Log gRPC exporter ignores env TLS certs, bypassing mTLS/pinning

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.3 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-81871: 0.20% estimated exploitation activity in the next 30 days; percentile 9.42 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The OTLP log gRPC exporter loads TLS settings from environment variables but does not apply them when creating gRPC transport credentials. Operators who rely on OTELEXPORTEROTLPLOGSCERTIFICATE, OTELEXPORTEROTLPCERTIFICATE, or related client certificate variables for CA pinning or mTLS get a connection that falls back to system roots and omits the env-supplied client certificate. A network attacker who can intercept or spoof the collector connection with a system-trusted certificate can read or alter log telemetry. Introduced in commit: d99c76f Details The affected code is in exporters/otlp/otlplog/otlploggrpc. newConfig resolves env-based TLS configuration into cfg.tlsCfg at exporters/otlp/otlplog/otlploggrpc/config.go:106-116. The finding also identifies loadEnvTLS at config.go:451-492 as the code that builds a tls.Config containing RootCAs and client certificates from OTELEXPORTEROTLP[LOGS]CERTIFICATE and OTELEXPORTEROTLP[LOGS]CLIENTCERTIFICATE/KEY. However,…

Published by the source

17 Sep 2026, 20:31 UTC

Last modified by the source

28 Sep 2026, 17:00 UTC

Source last checked

26 Oct 2026, 15:29 UTC

1. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w34q-cm8f-9c5x

2. Revision 3 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6508

4. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-w34q-cm8f-9c5x

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# Patch Next advisory brief: CVE-2026-81871

Advisory: OpenTelemetry-Go: Log gRPC exporter ignores env TLS certs, bypassing mTLS/pinning
IDs: CVE-2026-81871, GHSA-w34q-cm8f-9c5x
Record: https://patchnext.com/advisories/cve-2026-81871 (revision 4, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc 0.21.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc: affected < 0.21.0; fixed in 0.21.0

## Suggested inspection (read-only)
- Go go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-w34q-cm8f-9c5x (OSV record GHSA-w34q-cm8f-9c5x lists affected ranges: Go go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc >=0 <0.21.0 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6508 (OSV record GO-2026-6508 lists affected ranges: Go go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc >=0 <0.21.0 (fixed))
- Verified: https://github.com/advisories/GHSA-w34q-cm8f-9c5x (GitHub-reviewed advisory GHSA-w34q-cm8f-9c5x lists affected ranges: Go go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc >=0 <0.21.0)

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