CVE-2026-81869
OpenTelemetry-Go: UTF-8 replacement rune bypasses attribute length truncation
Impact
OpenTelemetry-Go is the Go implementation of OpenTelemetry. From version 1.10.0 until 1.33.0, the sdk/trace/span.go attribute truncation path can fail to enforce AttributeValueLengthLimit for string and string-slice attributes containing the valid Unicode replacement character U+FFFD. safeTruncateValidUTF8 treats the valid replacement rune as invalid UTF-8 and returns the original input, while strings.ToValidUTF8 leaves that valid rune unchanged, so a second safeTruncate attempt can also return the oversized value. An attacker who controls span attribute content can retain values longer than the configured limit, increasing per-span memory use and weakening denial-of-service protection in the instrumented process. This issue is fixed in version 1.33.0.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| go | go.opentelemetry.io/otel/sdk | >= 1.10.0, < 1.33.0 | 1.33.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-p9f8-wvj8-2fg8
- https://github.com/open-telemetry/opentelemetry-go/security/advisories/GHSA-p9f8-wvj8-2fg8
- https://nvd.nist.gov/vuln/detail/CVE-2026-81869
- https://github.com/open-telemetry/opentelemetry-go/issues/5996
- https://github.com/open-telemetry/opentelemetry-go/pull/5997
- https://github.com/open-telemetry/opentelemetry-go/commit/e016a78c9f5b24a1c2beeaad47686c2f2213f49a
- https://github.com/open-telemetry/opentelemetry-go/releases/tag/sdk/v1.33.0