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Medium, CVSS 5.3

OpenTelemetry dotnet: Excessive memory allocation when parsing OpenTelemetry propagation headers

CVE-2026-40894GHSA-g94r-2vxg-569j

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (opentelemetry.extensions.propagators 1.15.3; opentelemetry.api 1.15.3), 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
5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
EPSS
  • CVE-2026-40894: 0.46% estimated exploitation activity in the next 30 days; percentile 39.74 (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 implementation details of the baggage, B3 and Jaeger processing code in the OpenTelemetry.Api and OpenTelemetry.Extensions.Propagators NuGet packages can allocate excessive memory when parsing which could create a potential denial of service (DoS) in the consuming application. Details Exceeding Limits BaggagePropagator.Inject<T() does not enforce the length limit of 8192 characters if the injected baggage contains only one item. This change was introduced by #1048. Excessive allocation The following methods eagerly allocate intermediate arrays before applying size limits. - BaggagePropagator.Extract<T() - this change was introduced by #1048. - BaggagePropagator.Inject<T() - this change was introduced by #1048. - B3Propagator.Extract<T() - this change was introduced by #533. - B3Propagator.Extract<T() - this change was introduced by #3244. - JaegerPropagator.Extract<T() - this change was introduced by #3309. Impact Excessively large propagation headers, particularly in…

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

    Published from ghsa record GHSA-g94r-2vxg-569j

Agent brief

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# Patch Next advisory brief: CVE-2026-40894

Advisory: OpenTelemetry dotnet: Excessive memory allocation when parsing OpenTelemetry propagation headers
IDs: CVE-2026-40894, GHSA-g94r-2vxg-569j
Record: https://patchnext.com/advisories/cve-2026-40894 (revision 1, source checked 26 Oct 2026, 17:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: opentelemetry.extensions.propagators 1.15.3; opentelemetry.api 1.15.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet opentelemetry.extensions.propagators: affected >= 1.3.1, < 1.15.3; fixed in 1.15.3
- NuGet opentelemetry.api: affected >= 0.5.0-beta.2, < 1.15.3; fixed in 1.15.3

## Suggested inspection (read-only)
- NuGet opentelemetry.extensions.propagators: check the installed version with your package manager.
- NuGet opentelemetry.api: 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 opentelemetry.extensions.propagators, opentelemetry.api.
- 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://github.com/advisories/GHSA-g94r-2vxg-569j (GitHub-reviewed advisory GHSA-g94r-2vxg-569j lists affected ranges: NuGet opentelemetry.api >=0.5.0-beta.2 =1.3.1 <1.15.3)

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