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CVE-2021-21705— Incorrect URL validation in FILTER_VALIDATE_URL

Quick assessment

Affected
PHP Group PHP
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.

PHP是一种在服务器端执行的脚本语言。 PHP 存在输入验证错误漏洞，攻击者可利用该漏洞通过PHP的 FILTER_VALIDATE_URL 欺骗用户，以便将其重定向到恶意站点。

CVSS 4.3 · Medium EPSS 2.09% · P81
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I. Basic Information for CVE-2021-21705

Vulnerability Information
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Vulnerability Title
Incorrect URL validation in FILTER_VALIDATE_URL
Source: CVE Program / CVE List V5
Vulnerability Description
In PHP versions 7.3.x below 7.3.29, 7.4.x below 7.4.21 and 8.0.x below 8.0.8, when using URL validation functionality via filter_var() function with FILTER_VALIDATE_URL parameter, an URL with invalid password field can be accepted as valid. This can lead to the code incorrectly parsing the URL and potentially leading to other security implications - like contacting a wrong server or making a wrong access decision.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
EasyApache 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
PHP是一种在服务器端执行的脚本语言。 PHP 存在输入验证错误漏洞，攻击者可利用该漏洞通过PHP的 FILTER_VALIDATE_URL 欺骗用户，以便将其重定向到恶意站点。
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
PHP Group PHP 7.3.x ~ 7.3.29 -

II. Public POCs for CVE-2021-21705

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III. Intelligence Information for CVE-2021-21705

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Vendor Advisories for CVE-2021-21705 (3)

Other References for CVE-2021-21705 (1)

Same Patch Batch · PHP Group · 2021-10-04 · 3 CVEs total

CVE-2021-21706 5.3 MEDIUM ZipArchive::extractTo may extract outside of destination dir
CVE-2021-21704 5.0 MEDIUM Multiple vulnerabilities in Firebird client extension

IV. Related Vulnerabilities

Same product: PHP
Same vendor: PHP Group
Same weakness: CWE-20

V. Comments for CVE-2021-21705

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