GitHub Security Advisory: GHSA-g94r-2vxg-569j
Package: OpenTelemetry.Api (NUGET)
Severity: MODERATE (CVSS 5.3)
CWE: CWE-789: Memory Allocation with Excessive Size Value
Vulnerable versions: >= 0.5.0-beta.2, < 1.15.3
Patched in: 1.15.3

Summary: OpenTelemetry dotnet: Excessive memory allocation when parsing OpenTelemetry propagation headers

Details:
### 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>()`](https://github.com/open-telemetry/opentelemetry-dotnet/blob/fc1a2864d1665bda857089e11fe9247e3c75637a/src/OpenTelemetry.Api/Context/Propagation/BaggagePropagator.cs#L93-L112) 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>()`](https://github.com/open-telemetry/opentelemetry-dotnet/blob/888d1bf2489fb7408d3c5e8758a5bbffa89a8fb2/src/OpenTelemetry.Api/Context/Propagation/BaggagePropagator.cs#L52-L55) - this change was introduced by #1048.
- [`BaggagePropagator.Inject<T>()`](https://github.com/open-telemetry/opentelemetry-dotnet/blob/888d1bf2489fb7408d3c5e8758a5bbffa89a8fb2/src/OpenTelemetry.Api/Context/Propagation/BaggagePropagator.cs#L138-L157) - this change was introduced by #1048.
- [`B3Propagator.Extract<T>()`](https://github.com/open-telemetry/opentelemetry-dotnet/blob/888d1bf2489fb7408d3c5e8758a5bbffa89a8fb2/src/OpenTelemetry.Extensions.Propagators/B3Propagator.cs#L203-L207) - this change was introduced by #533.
- [`B3Propagator.Extract<T>()`](https://github.com/open-telemetry/opentelemetry-dotnet/blob/888d1bf2489fb7408d3c5e8758a5bbffa89a8fb2/src/OpenTelemetry.Api/Context/Propagation/B3Propagator.cs#L204-L214) - this change was introduced by #3244.
- [`JaegerPropagator.Extract<T>()`](https://github.com/open-telemetry/opentelemetry-dotnet/blob/888d1bf2489fb7408d3c5e8758a5bbffa89a8fb2/src/OpenTelemetry.Extensions.Propagators/JaegerPropagator.cs#L150-L154) - this change was introduced by #3309.

### Impact

Excessively large propagation headers, particularly in degenerate/malformed cases that consist or large numbers of delimiter characters, can allocate excessive amounts of memory for intermediate storage of parsed content relative to the size of the original input.

### Mitigation

HTTP servers often set maximum limits on the length of HTTP request headers, such as [Internet Information Services (IIS)](https://learn.microsoft.com/iis/configuration/system.webserver/security/requestfiltering/requestlimits/headerlimits/) which sets a default limit of 16KB and [nginx](https://nginx.org/docs/http/ngx_http_core_module.html#large_client_header_buffers) which sets a default limit of 8KB.

### Workarounds

Possible workarounds include:

- Configuring appropriate HTTP request header limits.
- Disabling baggage and/or trace propagation.

### Remediation

[#7061](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7061) refactors the handling of bag