CVE-2025-53094

ESPAsyncWebServer Vulnerable to CRLF Injection in AsyncWebHeader.cpp

State: Published
Severity: 8.7 High
Published: Jun 27, 2025
Updated: Jun 27, 2025
Reserved: Jun 25, 2025

Description

ESPAsyncWebServer is an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350. In versions up to and including 3.7.8, a CRLF (Carriage Return Line Feed) injection vulnerability exists in the construction and output of HTTP headers within `AsyncWebHeader.cpp`. Unsanitized input allows attackers to inject CR (`\r`) or LF (`\n`) characters into header names or values, leading to arbitrary header or response manipulation. Manipulation of HTTP headers and responses can enable a wide range of attacks, making the severity of this vulnerability high. A fix is available at pull request 211 and is expected to be part of version 3.7.9.

Scores

CVSS	Score	Vector	Source
4.0	8.7 High	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N	GitHub_M

Weaknesses

CWE-93 Improper Neutralization of CRLF Sequences ('CRLF Injection')
CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')

Affected Products

Product	Versions
ESPAsyncWebServerESP32Async	<= 3.7.8Affected

References

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