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    CVE-2026-55599

    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.

    Published:Jun 22, 2026
    Last Modified:Jun 23, 2026
    EPS:Jun 22, 2026
    EPSS Score:0.00128
    CVSS Score:5.8

    Affected Products

    Vendor
    Phpseclib
    Product
    Phpseclib

    Exploits

    https://github.com/phpseclib/phpseclib/security/advisories/GHSA-m557-wrgg-6rp4https://github.com/phpseclib/phpseclib/security/advisories/GHSA-m557-wrgg-6rp4

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-664 Server Side Request Forgery

    Related CVEs

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    CVE-2026-40194 (CVSS 3.7) — phpseclib is a PHP secure communications library. Starting in 0.1.1 and prior to 3.0.51, 2.0.53, and 1.0.28, p…
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    CVE-2023-52892 (CVSS 7.5) — In phpseclib before 1.0.22, 2.x before 2.0.46, and 3.x before 3.0.33, some characters in Subject Alternative N…
    CVE-2024-27355 (CVSS 7.5) — An issue was discovered in phpseclib 1.x before 1.0.23, 2.x before 2.0.47, and 3.x before 3.0.36. When process…
    CVE-2024-27354 (CVSS 7.5) — An issue was discovered in phpseclib 1.x before 1.0.23, 2.x before 2.0.47, and 3.x before 3.0.36. An attacker …
    CVE-2023-49316 (CVSS 7.5) — In Math/BinaryField.php in phpseclib 3 before 3.0.34, excessively large degrees can lead to a denial of servic…
    CVE-2023-27560 (CVSS 7.5) — Math/PrimeField.php in phpseclib 3.x before 3.0.19 has an infinite loop with composite primefields.…
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    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High