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Medium, CVSS 5.1amended

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

CVE-2026-81869GHSA-p9f8-wvj8-2fg8

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (go.opentelemetry.io/otel/sdk 1.33.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
5.1 · 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 · score source
EPSS
  • CVE-2026-81869: 0.18% estimated exploitation activity in the next 30 days; percentile 7.61 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 4 · amended ·

    Amended from ghsa record GHSA-p9f8-wvj8-2fg8

  2. Revision 3 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 2 · amended ·

    Amended from osv record GO-2026-6616

  4. Revision 1 · created ·

    Published from osv record GHSA-p9f8-wvj8-2fg8

Agent brief

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# Patch Next advisory brief: CVE-2026-81869

Advisory: OpenTelemetry-Go: UTF-8 replacement rune bypasses attribute length truncation
IDs: CVE-2026-81869, GHSA-p9f8-wvj8-2fg8
Record: https://patchnext.com/advisories/cve-2026-81869 (revision 4, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: go.opentelemetry.io/otel/sdk 1.33.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go go.opentelemetry.io/otel/sdk: affected >= 1.10.0, < 1.33.0; fixed in 1.33.0

## Suggested inspection (read-only)
- Go go.opentelemetry.io/otel/sdk: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on go.opentelemetry.io/otel/sdk.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6616 (OSV record GO-2026-6616 lists affected ranges: Go go.opentelemetry.io/otel/sdk >=1.10.0 <1.33.0 (fixed))
- Verified: https://osv.dev/vulnerability/GHSA-p9f8-wvj8-2fg8 (OSV record GHSA-p9f8-wvj8-2fg8 lists affected ranges: Go go.opentelemetry.io/otel/sdk >=1.10.0 <1.33.0 (fixed))
- Verified: https://github.com/advisories/GHSA-p9f8-wvj8-2fg8 (GitHub-reviewed advisory GHSA-p9f8-wvj8-2fg8 lists affected ranges: Go go.opentelemetry.io/otel/sdk >=1.10.0 <1.33.0)

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