CVE-2026-28898: Apple swift-nio-http2 request smuggling in HTTP2ToHTTP1Codec

CVE-2026-28898 · Severity: low · CVSS 0 · Published 2026-06-25

Apple's swift-nio-http2 library, used for building high-performance networking applications in Swift, contains a vulnerability in how it converts modern HTTP/2 traffic into older HTTP/1.1 format. An attacker can send specially crafted web requests that "smuggle" hidden commands past security filters. This can lead to unauthorized access to data, bypass of security controls, or interference with other users' web sessions when the library is used in proxy or server environments.

Technologies: Apple SwiftNIO HTTP2. Vendors: Apple, Swift.

Quick answers

Is CVE-2026-28898 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-28898 being exploited in the wild.
How severe is CVE-2026-28898?
Low severity, with a CVSS score of 0, published 25 June 2026.
Which products and versions are affected?
github.com/apple/swift-nio-http2 (Swift) < 1.44.1.
Is there a fix for CVE-2026-28898?
A patch was published on 2026-06-25: Fix released in version 1.44.1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-28898 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-28898?
Check whether you run Apple SwiftNIO HTTP2 or github.com/apple/swift-nio-http2 (Swift) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A request smuggling vulnerability exists in the HTTP2ToHTTP1Codec of swift-nio-http2. The codec fails to validate pseudo-header values (such as :path, :authority, and :method) for control characters like CR, LF, or NUL before translating them into HTTP/1.1 messages. Because HTTP/2 uses binary framing, these characters are passed transparently, but they act as delimiters when converted to the text-based HTTP/1.1 protocol. A remote, unauthenticated attacker can exploit this to inject headers or smuggle entire requests to backend servers. The issue is resolved in version 1.44.1 by adding validation at both the HPACK and translation layers.

Affected products

  • Apple swift-nio-http2 < 1.44.1

Identifiers

  • CVE-2026-28898
  • GHSA-4px2-pw77-vc85

Timeline

  • 2026-05-21: disclosed: Advisory published by Apple on GitHub
  • 2026-06-25: advisory: NVD publication date
  • 2026-06-25: patched: Fix released in version 1.44.1

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