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CVE-2026-55599— phpseclib: X.509 certificate validation sends attacker-controlled outbound requests (server-side request forgery) via Authority Information Access

Quick assessment

Affected
phpseclib phpseclib
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.

phpseclib是phpseclib组织开源的一个 PHP 安全通信库。 phpseclib存在服务端请求伪造漏洞，该漏洞源于不安全默认设置，在验证不可信X.509证书时从证书的AIA扩展中读取URL并连接，可能导致未经身份验证的攻击者使验证服务器向内部主机和端口发起连接，造成服务端请求伪造。

CVSS 5.8 · Medium EPSS 0.21% · P11

Affected Version Matrix 3

VendorProduct Version RangeStatus
phpseclib phpseclib >= 0.1.1, < 1.0.30 affected
>= 2.0.0, < 2.0.55 affected
>= 3.0.0, < 3.0.54 affected
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I. Basic Information for CVE-2026-55599

Vulnerability Information
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Vulnerability Title
phpseclib: X.509 certificate validation sends attacker-controlled outbound requests (server-side request forgery) via Authority Information Access
Source: CVE Program / CVE List V5
Vulnerability Description
phpseclib is a PHP secure communications library. From 0.1.1 until 1.0.30, 2.0.55, and 3.0.54, when an application validates an untrusted X.509 certificate with phpseclib, X509::validateSignature() reads a URL out of that certificate's Authority Information Access (AIA) extension and connects to it. Attacker who supplies certificate fully controls host, port, and path of that connection. URL fetching is enabled by default, and no destination is blocked. An unauthenticated attacker can therefore make a validating server open connections to internal hosts and ports it should never reach, for example loopback 127.0.0.1, cloud metadata address 169.254.169.254, and internal-only services. This is a server-side request forgery (SSRF) caused by an insecure default. This vulnerability is fixed in 1.0.30, 2.0.55, and 3.0.54.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
phpseclib 服务端请求伪造漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
phpseclib是phpseclib组织开源的一个 PHP 安全通信库。 phpseclib存在服务端请求伪造漏洞，该漏洞源于不安全默认设置，在验证不可信X.509证书时从证书的AIA扩展中读取URL并连接，可能导致未经身份验证的攻击者使验证服务器向内部主机和端口发起连接，造成服务端请求伪造。
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
phpseclib phpseclib >= 0.1.1, < 1.0.30 -

II. Public POCs for CVE-2026-55599

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III. Intelligence Information for CVE-2026-55599

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Vendor Advisories for CVE-2026-55599 (1)

IV. Related Vulnerabilities

Same product: phpseclib
Same vendor: phpseclib
Same weakness: CWE-918

V. Comments for CVE-2026-55599

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