What’s Vulnerable › Vulnerabilities

CVE-2026-81869: OpenTelemetry-Go: UTF-8 replacement rune bypasses attribute length truncation

• Severity: medium (CVSS 5.1 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-16 · updated 2026-09-30
• Weakness: CWE-176

Description

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 products

• open-telemetry opentelemetry-go: from 1.10.0, < 1.33.0

References

• https://github.com/open-telemetry/opentelemetry-go/commit/e016a78c9f5b24a1c2beeaad47686c2f2213f49a
• 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/releases/tag/sdk/v1.33.0
• https://github.com/open-telemetry/opentelemetry-go/security/advisories/GHSA-p9f8-wvj8-2fg8
• https://github.com/open-telemetry/opentelemetry-go/security/advisories/GHSA-p9f8-wvj8-2fg8

Get alerted when CVE-2026-81869 or the next vulnerability affects your stack