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CVE-2026-42855— arduino-esp32: Digest authentication URI mismatch bypass in WebServer allows cross-resource replay attack

Quick assessment

Affected
espressif arduino-esp32
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

arduino-esp32是Espressif开源的一个用于 ESP32、ESP32-S2、ESP32-S3、ESP32-C3、ESP32-C6 和 ESP32-H2 的 Arduino 内核。 arduino-esp32 3.3.8之前版本存在授权问题漏洞，该漏洞源于WebServer摘要认证实现使用客户端Authorization标头中的URI字段计算认证哈希而不验证其与实际请求URI匹配，可能导致绕过每资源访问控制。

CVSS 7.5 · High EPSS 0.51% · P42

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
espressif arduino-esp32 < 3.3.8 affected
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I. Basic Information for CVE-2026-42855

Vulnerability Information
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Vulnerability Title
arduino-esp32: Digest authentication URI mismatch bypass in WebServer allows cross-resource replay attack
Source: CVE Program / CVE List V5
Vulnerability Description
arduino-esp32 is an Arduino core for the ESP32, ESP32-S2, ESP32-S3, ESP32-C3, ESP32-C6 and ESP32-H2 microcontrollers. Prior to 3.3.8, the WebServer Digest authentication implementation in arduino-esp32 computes the authentication hash using the URI field from the client's Authorization header, without verifying that it matches the actual requested URI. This allows an attacker who possesses any valid digest response (computed for URI-A) to authenticate requests to a completely different protected URI (URI-B), bypassing per-resource access control. This vulnerability is fixed in 3.3.8.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
arduino-esp32 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
arduino-esp32是Espressif开源的一个用于 ESP32、ESP32-S2、ESP32-S3、ESP32-C3、ESP32-C6 和 ESP32-H2 的 Arduino 内核。 arduino-esp32 3.3.8之前版本存在授权问题漏洞，该漏洞源于WebServer摘要认证实现使用客户端Authorization标头中的URI字段计算认证哈希而不验证其与实际请求URI匹配，可能导致绕过每资源访问控制。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
espressif arduino-esp32 < 3.3.8 -

II. Public POCs for CVE-2026-42855

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III. Intelligence Information for CVE-2026-42855

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Vendor Advisories for CVE-2026-42855 (1)

IV. Related Vulnerabilities

Same product: arduino-esp32
Same vendor: espressif
Same weakness: CWE-287

V. Comments for CVE-2026-42855

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