Bug 2535728 (CVE-2026-81869)

Summary: CVE-2026-81869 github.com/open-telemetry/opentelemetry-go: OpenTelemetry-Go: Denial of Service via attribute length truncation bypass
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in OpenTelemetry-Go. An attacker who can control span attribute content can bypass the attribute length truncation mechanism. This occurs when string attributes contain the Unicode replacement character U+FFFD, preventing the enforcement of configured memory limits. This vulnerability allows for increased memory usage per span, which can weaken denial-of-service protection in the instrumented process.
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Description OSIDB Bzimport 2026-09-16 21:13:34 UTC 
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.