CVE-2026-64785: Request Smuggling (CVSS 5.3)

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.

Is your site exposed to CVE-2026-64785?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

5.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS — Exploit Prediction

0.0018

Probability of exploitation

0.08%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-444 CWE-444

References

Other References

https://github.com/apple/swift-nio-http2/security/advisories/GHSA-q3g2-m552-3r9c

Frequently Asked Questions

What is CVE-2026-64785? +

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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-64785? +

CVE-2026-64785 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0018, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-64785? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-1867

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in ithewei libhv allows HTTP Response Smuggling.This issue affects libhv: through …

CVE-2024-23316

HTTP request desynchronization in Ping Identity PingAccess, all versions prior to 8.0.1 affected allows an attacker to send specially crafted …

CVE-2024-38494

This vulnerability allows a high-privileged authenticated PAM user to achieve remote command execution on the affected PAM system by sending …

CVE-2025-6999

An HTTP Request Smuggling [CWE-444] vulnerability in the Authentication portal of WatchGuard Fireware OS allows a remote attacker to evade …

CVE-2025-11915

Connection desynchronization between an HTTP proxy and the model backend. The fixes were rolled out for all proxies in front …

CVE-2023-53878

Member Login Script 3.3 contains a client-side desynchronization vulnerability that allows attackers to manipulate HTTP request handling by exploiting Content-Length …

CVE-2026-64785