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

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

OpenTelemetry-Go is the Go implementation of OpenTelemetry. Prior to version 0.21.0, the exporters/otlp/otlplog/otlploggrpc package loads OTEL_EXPORTER_OTLP_LOGS_CERTIFICATE, OTEL_EXPORTER_OTLP_CERTIFICATE, and related client certificate environment variables through loadEnvTLS into cfg.tlsCfg, but newGRPCDialOptions does not apply cfg.tlsCfg when creating gRPC transport credentials. The environment-only TLS path instead uses credentials.NewTLS with system roots and no configured client certificate, bypassing intended private CA pinning and mutual TLS unless the application also supplies WithTLSCredentials. A network attacker able to intercept or spoof the collector connection with a system-trusted certificate can read or alter log telemetry. This issue is fixed in version 0.21.0.

Source published

16 Sep 2026 20:43:40 UTC

Source modified

17 Sep 2026 19:24:00 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

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

OpenTelemetry-Go is the Go implementation of OpenTelemetry. Prior to version 0.21.0, the exporters/otlp/otlplog/otlploggrpc package loads OTEL_EXPORTER_OTLP_LOGS_CERTIFICATE, OTEL_EXPORTER_OTLP_CERTIFICATE, and related client certificate environment variables through loadEnvTLS into cfg.tlsCfg, but newGRPCDialOptions does not apply cfg.tlsCfg when creating gRPC transport credentials. The environment-only TLS path instead uses credentials.NewTLS with system roots and no configured client certificate, bypassing intended private CA pinning and mutual TLS unless the application also supplies WithTLSCredentials. A network attacker able to intercept or spoof the collector connection with a system-trusted certificate can read or alter log telemetry. This issue is fixed in version 0.21.0.

Source published

Sep 16, 2026, 8:43:40 PM (timezone not stated)

Source modified

Sep 17, 2026, 7:24:00 PM (timezone not stated)

Observed here

11 Nov 2026 16:10:31 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD 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

OpenTelemetry-Go is the Go implementation of OpenTelemetry. Prior to version 0.21.0, the exporters/otlp/otlplog/otlploggrpc package loads OTEL_EXPORTER_OTLP_LOGS_CERTIFICATE, OTEL_EXPORTER_OTLP_CERTIFICATE, and related client certificate environment variables through loadEnvTLS into cfg.tlsCfg, but newGRPCDialOptions does not apply cfg.tlsCfg when creating gRPC transport credentials. The environment-only TLS path instead uses credentials.NewTLS with system roots and no configured client certificate, bypassing intended private CA pinning and mutual TLS unless the application also supplies WithTLSCredentials. A network attacker able to intercept or spoof the collector connection with a system-trusted certificate can read or alter log telemetry. This issue is fixed in version 0.21.0.

Source published

16 Sep 2026 21:17:22 UTC

Source modified

30 Sep 2026 17:31:44 UTC

Observed here

25 Oct 2026 16:19:10 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

### 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 `OTEL_EXPORTER_OTLP_LOGS_CERTIFICATE`, `OTEL_EXPORTER_OTLP_CERTIFICATE`, 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 `OTEL_EXPORTER_OTLP[_LOGS]_CERTIFICATE` and `OTEL_EXPORTER_OTLP[_LOGS]_CLIENT_CERTIFICATE`/`KEY`. However, `newGRPCDialOptions` in `exporters/otlp/otlplog/otlploggrpc/client.go:83-92` only checks `cfg.gRPCCredentials` and `cfg.insecure`. When neither is set, which is the normal env-only TLS configuration path, it uses `credentials.NewTLS(nil)`. That default trusts the host system root CAs and contains no env-supplied client certificate. The finding evidence reports no other `tlsCfg` use in the package, so env-based CA pinning and mTLS settings are loaded but not enforced. ### PoC [validation-artifact.zip](https://github.com/user-attachments/files/27493589/validation-artifact.zip) The validation artifact contains a ready-to-run test at `validation-artifact.zip:./poc_env_tls_ignored_test.go` and brief instructions at `validation-artifact.zip:./README.md`. From a checkout of `pellared/opentelemetry-go` at commit `d99c76f`, with Go module dependencies available: ```sh FINDING_DIR=/path/to/02-e6e2897a969c8191b260f243fbc99ebd-log-grpc-exporter-ignores-env-tls-certs-bypassing-mtls-pinning cd /path/to/opentelemetry-go git checkout d99c76f tar -xOf validation-artifact.tar ./poc_env_tls_ignored_test.go > exporters/otlp/otlplog/otlploggrpc/poc_env_tls_ignored_test.go cd exporters/otlp/otlplog/otlploggrpc GO111MODULE=on go test -v -run TestEnvTLSIgnored -count=1 ``` The test generates a private CA and a TLS gRPC logs server certificate signed by that CA. It sets: ```sh OTEL_EXPORTER_OTLP_LOGS_ENDPOINT=https://127.0.0.1:<test-port> OTEL_EXPORTER_OTLP_LOGS_CERTIFICATE=<temp-dir>/ca.pem ``` Expected output includes an `unknown authority` failure for the first export call even though the env certificate points to the server CA, followed by a passing test after the same `cfg.tlsCfg` is explicitly wired through `WithTLSCredentials`: ```text === RUN TestEnvTLSIgnored poc_env_tls_ignored_test.go:...: export error (expected due to ignored tlsCfg): ... x509: certificate signed by unknown authority --- PASS: TestEnvTLSIgnored PASS ``` This demonstrates that the env CA is parsed into `cfg.tlsCfg` but ignored by the default gRPC dial path. ### Impact This is improper TLS certificate validation and endpoint authentication caused by ignoring configured trust material. Users of the OTLP log gRPC exporter who configure TLS, CA pinning, or mTLS through environment variables are impacted when they do not also supply explicit `WithTLSCredentials`. TLS still occurs with system roots, but the intended private CA pinning and client certificate authentication are bypassed. An attacker with a suitable network position and a system-trusted certificate for the collector endpoint can intercept or tamper with log telemetry that operators expected to be protected by the configured CA or mTLS policy.

Source published

17 Sep 2026 20:31:09 UTC

Source modified

28 Sep 2026 17:10:47 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · 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

Publisher rating · MODERATE

OpenTelemetry-Go: Log gRPC exporter ignores env TLS certs, bypassing mTLS/pinning in go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc

Source published

28 Sep 2026 16:43:40 UTC

Source modified

28 Sep 2026 17:00:16 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.