CVE-2026-23886 Swift W3C TraceContext has malformed HTTP header that can cause a crash

What is CVE-2026-23886?

CVE-2026-23886 is a medium-severity denial of service vulnerability in swift-otel swift-w3c-trace-context, published on 19 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Swift W3C TraceContext is a Swift implementation of the W3C Trace Context standard, and Swift OTel is an OpenTelemetry Protocol (OTLP) backend for Swift Log, Swift Metrics, and Swift Distributed Tracing. Prior to Swift W3C TraceContext version 1.0.0-beta.5 and Swift OTel version 1.0.4, a denial-of-service vulnerability due to improper input validation allows a remote attacker to crash the service via a malformed HTTP header. This allows crashing the process with data coming from the network when used with, for example, an HTTP server. Most common way of using Swift W3C Trace Context is through Swift OTel. Version 1.0.0-beta.5 of Swift W3C TraceContext and version 1.0.4 of Swift OTel contain a patch for this issue. As a workaround, disable either Swift OTel or the code that extracts the trace information from an incoming header (such as a `TracingMiddleware`).

Weakness: CWE-20

Which versions are affected by CVE-2026-23886?

4 open source packages ship an affected version, including github.com/swift-otel/swift-w3c-trace-context and github.com/swift-otel/swift-otel.

How do I fix CVE-2026-23886?

Upgrade github.com/swift-otel/swift-w3c-trace-context to 1.0.0-beta.5 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-23886 being exploited?

There is no known exploitation of CVE-2026-23886 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-mvpq-2v8x-ww6g.