SEPTEMBER 19, 2026
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Case File

CVE-2026-18174

MEDIUM · CVSS 5.3 EPSS 0.19% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-07-29 · Last synced 2026-08-28

CyberRota Analysis

AI-Generated

The vulnerability affects the @fastify/forwarded package, specifically in versions prior to 3.0.2, where improper handling of the X-Forwarded-For header allows for the inclusion of horizontal tabs in client IP addresses. This can lead to security evasion in applications that rely on exact string matches for IP-based security measures, such as allowlists or rate limiting. Organizations using affected versions should prioritize upgrading to 3.0.2 or later to mitigate potential security risks.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

GitHub PoC Links

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-18174
Severity
MEDIUM
CVSS
5.3
EPSS
0.19%

Original NVD Description

@fastify/forwarded resolves client addresses from the X-Forwarded-For header. In versions before 3.0.2, when the header contains two or more comma separated entries, the parser trims only space characters and does not strip horizontal tabs, even though RFC 7230 defines optional whitespace as both space and tab. As a result, an entry padded with a tab keeps the literal tab in the resolved address string. Applications that make exact string match security decisions on the resolved client IP, such as an allowlist, a blocklist, a per IP rate limit key, or audit log correlation, can be evaded because the tab corrupted string no longer matches the expected value. This does not cross the trust boundary, since a tab corrupted string is not a valid IP and cannot be mistaken for a trusted proxy. The issue is fixed in @fastify/forwarded 3.0.2.

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