Vulnerability in go.opentelemetry.io/otel/sdk (CVE-2026-81869)
Summary
Vulnerability in go.opentelemetry.io/otel/sdk (CVE-2026-81869). Risk of unauthorized operations or information disclosure. Exploitable via AttributeValueLengthLimit. Mitigation: upgrade to 1.33.0 or later.
Original description
The description as published by the source.
Summary
The OpenTelemetry Go SDK trace package can fail to enforce AttributeValueLengthLimit for string attributes containing the valid Unicode replacement character U+FFFD. An oversized attacker-controlled attribute value that includes U+FFFD is returned untruncated, bypassing the configured memory/DoS protection and allowing increased per-span memory usage. The finding is low severity because it requires a deployment with attribute value length limits enabled and attacker-controlled data being recorded into span attributes.
Introduced in commit 49a6536
Details
String and string-slice span attributes are truncated through safeTruncate when AttributeValueLengthLimit is non-negative. The finding evidence identifies this enforcement path in sdk/trace/span.go:303-331, with string attributes passed to safeTruncate at sdk/trace/span.go:309-310 and string-slice entries passed to safeTruncate in the loop beginning at sdk/trace/span.go:312.
safeTruncate first calls safeTruncateValidUTF8; if that returns ok=false, it calls strings.ToValidUTF8(input, "") and retries. The relevant code is identified in sdk/trace/span.go:337-355. safeTruncateValidUTF8 treats any utf8.RuneError from utf8.DecodeRuneInString as invalid UTF-8 and immediately returns the original input with ok=false. However, Go also returns utf8.RuneError for a valid encoded U+FFFD rune. The validation artifact confirms this behavior with output `r=U+FFFD size=3 runeError=true…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-81869 has been found in go.opentelemetry.io/otel/sdk.
Attackers can target a specific entry point like AttributeValueLengthLimit over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade go.opentelemetry.io/otel/sdk to 1.33.0 or later.
If unsure, ask your IT team or search "go.opentelemetry.io/otel/sdk CVE-2026-81869" on the vendor's site.
CVE-2026-81869 (go.opentelemetry.io/otel/sdk) — CWE-176
Attack surface: AttributeValueLengthLimit / safeTruncate / safeTruncateValidUTF8 / utf8.RuneError
Patched: 1.33.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-176) exists in go.opentelemetry.io/otel/sdk. Attackers reach the vulnerable code path via AttributeValueLengthLimit.
Check the vendor advisory for the affected versions of go.opentelemetry.io/otel/sdk. Attack surface: AttributeValueLengthLimit / safeTruncate / safeTruncateValidUTF8 / utf8.RuneError.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 1.33.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'go.opentelemetry.io/otel/sdk' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'go.opentelemetry.io/otel/sdk' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
go.opentelemetry.io/otel/sdkを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade go.opentelemetry.io/otel/sdk to 1.33.0ステージング環境で 1.33.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-81869 golang-opentelemetry-otel
- Ubuntu UBUNTU-CVE-2026-81869 golang-opentelemetry-otel
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com