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

Quick assessment

Affected
open-telemetry opentelemetry-go
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

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 repl

CVSS 5.1 · Medium

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2026-81869

Vulnerability Information
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Vulnerability Title
OpenTelemetry-Go: UTF-8 replacement rune bypasses attribute length truncation
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
Unicode编码处理不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
open-telemetry opentelemetry-go >= 1.10.0, < 1.33.0 -

II. Public POCs for CVE-2026-81869

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III. Intelligence Information for CVE-2026-81869

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Patches & Fixes for CVE-2026-81869 (2)

Other References for CVE-2026-81869 (3)

Same Patch Batch · open-telemetry · 2026-09-16 · 4 CVEs total

CVE-2026-81872 6.3 MEDIUM OpenTelemetry-Go: BatchProcessor can busy-spin when export buffer is full
CVE-2026-81871 6.3 MEDIUM OpenTelemetry-Go: Log gRPC exporter ignores env TLS certs, bypassing mTLS/pinning
CVE-2026-81870 2.0 LOW OpenTelemetry-Go: Exporter config logging may leak endpoint URLs in info logs

IV. Related Vulnerabilities

Same product: opentelemetry-go
Same vendor: open-telemetry
Same weakness: CWE-176

V. Comments for CVE-2026-81869

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