CVE-2026-41178

https://github.com/open-telemetry/opentelemetry-go/pull/7880 removed raw-length rejection and it causes Parse to process arbitrarily large/invalid baggage headers and log errors, enabling DoS via oversized inputs.

Details

The commit removes the upfront baggage-string length check and the per-member size guard in parsing. Parse now walks the entire input with strings.SplitSeq and skips invalid members while continuing to process the rest. For very large or malformed baggage headers, the parser still fully tokenizes and percent-decodes each member, and errors are forwarded to the global error handler (default logging). This lets a remote client send oversized/invalid headers to trigger excessive CPU/memory work and potentially large log output before any size limit is enforced, creating a denial-of-service risk in services that do not already enforce strict header size limits.

Summary:

• In baggage/baggage.go, parseMember performs full parsing and PathUnescape on the entire member without any size guard, amplifying work for large inputs. Parse no longer checks bStr length and continues processing invalid members, so oversized/invalid headers are fully parsed instead of being rejected early.
• In propagation/baggage.go, parsing errors from attacker-controlled headers are sent to the global error handler (default logging), which can amplify oversized-input impact.

PoC

baggage_dos_poc.tar.gz

The issue is reachable through standard propagation parsing (in-scope) and can be exploited remotely to cause CPU/log amplification, but the impact is availability-only and bounded by transport header limits and configurable error handling, supporting a medium severity rather than high/critical.

baggage.Parse iterates over all list members with strings.SplitSeq and skips invalid members while continuing, without a raw-length guard. parseMember performs full parsing and PathUnescape on each member, and propagation.Baggage forwards parsing errors to the global error handler, which logs by default. A remote client can therefore send oversized/invalid baggage headers that bypass the 8KB limit for valid members, causing extra CPU work and large log output, resulting in availability/log amplification in services that accept large headers and use the default handler.

Assumptions:

• An instrumented service uses the OpenTelemetry baggage propagator for inbound request parsing.
• Attackers can send oversized or malformed baggage headers that pass the hosting server/proxy header size limits.
• The default error handler is used or logs are otherwise emitted for parse errors.
• Inbound request parsing with propagation.Baggage
• Oversized/invalid baggage headers accepted by the HTTP/gRPC stack
• Error handler not suppressing parse errors

CVE-2026-41178 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.42.0, 1.44.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-41178? CVE-2026-41178 is a medium-severity security vulnerability in go.opentelemetry.io/otel/baggage (go), affecting versions = 1.41.0. It is fixed in 1.42.0, 1.44.0.
2. How severe is CVE-2026-41178? CVE-2026-41178 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2026-41178?
   • go.opentelemetry.io/otel/baggage (go) (versions = 1.41.0)
   • go.opentelemetry.io/otel/propagation (go) (versions = 1.41.0)
4. Is there a fix for CVE-2026-41178? Yes. CVE-2026-41178 is fixed in 1.42.0, 1.44.0. Upgrade to this version or later.
5. Is CVE-2026-41178 exploitable, and should I be worried? Whether CVE-2026-41178 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-41178 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-41178?
   • Upgrade go.opentelemetry.io/otel/baggage to 1.42.0 or later
   • Upgrade go.opentelemetry.io/otel/propagation to 1.42.0 or later
   • Upgrade go.opentelemetry.io/otel/baggage to 1.44.0 or later
   • Upgrade go.opentelemetry.io/otel/propagation to 1.44.0 or later