Description
SwiftNIO HTTP/2 was missing validation on inbound HEADERS frames that let CR, LF, NUL, SP and other control characters reach an HTTP/1.1 backend through NIOHTTP2's HTTP/2-to-HTTP/1 codec, enabling HTTP request smuggling or response splitting. This vulnerability is addressed in swift-nio-http2 version 1.45.0.
Published: 2026-07-23
Score: 5.3 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

SwiftNIO HTTP/2 lacked validation on inbound HEADERS frames, allowing control characters such as CR, LF, NUL, and SPACE to pass through the HTTP/2-to-HTTP/1 codec and reach an HTTP/1.1 backend. This flaw can enable HTTP request smuggling or response splitting attacks, potentially bypassing security controls or hijacking sessions by manipulating the request/response stream.

Affected Systems

Apple SwiftNIO HTTP/2 implementations with a version earlier than 1.45.0 are affected. The vulnerability applies to all environments that use the SwiftNIO HTTP/2 library without the patch released in version 1.45.0.

Risk and Exploitability

The CVSS score of 5.3 indicates moderate severity, while the EPSS score of less than 1% suggests a very low likelihood of exploitation at this time. The flaw is not listed in the CISA KEV catalog. Attacks would require an attacker to control the inbound traffic to the targeted H2/HTTP service, making the attack vector primarily network-based and potentially constrained to environments with exposed HTTP/2 interfaces.

Generated by OpenCVE AI on August 2, 2026 at 15:20 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Upgrade Apple swift-nio-http2 to version 1.45.0 or later.
  • Configure reverse proxies or firewalls to reject or sanitize CR, LF, NUL, and SPACE characters in inbound HEADERS frames before they are forwarded to the backend.
  • Deploy a strict HTTP/2 validation layer that enforces RFC compliance to prevent request smuggling and response splitting at the front‑end.

Generated by OpenCVE AI on August 2, 2026 at 15:20 UTC.

Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-q3g2-m552-3r9c swift-nio-http2: Missing CR/LF/NUL validation in header values
History

Fri, 31 Jul 2026 00:15:00 +0000

Type Values Removed Values Added
Title Missing Validation on HTTP/2 HEADERS Enables Request Smuggling swift-nio-http2: SwiftNIO HTTP/2: HTTP Request Smuggling and Response Splitting via Incomplete Header Validation
Weaknesses CWE-93
References
Metrics threat_severity

None

 threat_severity

Low

Tue, 28 Jul 2026 20:30:00 +0000

Type Values Removed Values Added
First Time appeared Apple
Apple swiftnio Http/2
Vendors & Products Apple
Apple swiftnio Http/2

Sun, 26 Jul 2026 04:45:00 +0000

Type Values Removed Values Added
Title Missing Validation on HTTP/2 HEADERS Enables Request Smuggling

Fri, 24 Jul 2026 20:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-444
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Thu, 23 Jul 2026 21:45:00 +0000

Type Values Removed Values Added
Description SwiftNIO HTTP/2 was missing validation on inbound HEADERS frames that let CR, LF, NUL, SP and other control characters reach an HTTP/1.1 backend through NIOHTTP2's HTTP/2-to-HTTP/1 codec, enabling HTTP request smuggling or response splitting. This vulnerability is addressed in swift-nio-http2 version 1.45.0.
References

Subscriptions

Apple Swiftnio Http/2
cve-icon MITRE

Status: PUBLISHED

Assigner: apple

Published:

Updated: 2026-07-24T20:06:58.518Z

Reserved: 2026-07-20T18:11:03.398Z

Link: CVE-2026-64785

cve-icon Vulnrichment

Updated: 2026-07-24T20:05:52.056Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-07-23T20:17:21.440

Modified: 2026-07-24T21:16:45.877

Link: CVE-2026-64785

cve-icon Redhat

Severity : Low

Publid Date: 2026-07-23T18:50:40Z

Links: CVE-2026-64785 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-08-02T15:30:17Z

Weaknesses
  • CWE-444

    Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

  • CWE-93

    Improper Neutralization of CRLF Sequences ('CRLF Injection')