phpseclib up to 1.0.29/2.0.54/3.0.53 X.509 Certificate X509::validateSignature server-side request forgery

Summaryinfo

A vulnerability classified as critical was found in phpseclib up to 1.0.29/2.0.54/3.0.53. Impacted is the function X509::validateSignature of the component X.509 Certificate Handler. Such manipulation leads to server-side request forgery. This vulnerability is documented as CVE-2026-55599. The attack can be executed remotely. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in phpseclib up to 1.0.29/2.0.54/3.0.53. It has been rated as critical. Affected by this issue is the function X509::validateSignature of the component X.509 Certificate Handler. The manipulation with an unknown input leads to a server-side request forgery vulnerability. Using CWE to declare the problem leads to CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-55599 since 06/17/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit.

Upgrading to version 1.0.30, 2.0.55 or 3.0.54 eliminates this vulnerability.

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Productinfo

Name

• phpseclib

Version

• 1.0.0
• 1.0.1
• 1.0.2
• 1.0.3
• 1.0.4
• 1.0.5
• 1.0.6
• 1.0.7
• 1.0.8
• 1.0.9
• 1.0.10
• 1.0.11
• 1.0.12
• 1.0.13
• 1.0.14
• 1.0.15
• 1.0.16
• 1.0.17
• 1.0.18
• 1.0.19
• 1.0.20
• 1.0.21
• 1.0.22
• 1.0.23
• 1.0.24
• 1.0.25
• 1.0.26
• 1.0.27
• 1.0.28
• 1.0.29
• 2.0.0
• 2.0.1
• 2.0.2
• 2.0.3
• 2.0.4
• 2.0.5
• 2.0.6
• 2.0.7
• 2.0.8
• 2.0.9
• 2.0.10
• 2.0.11
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• 2.0.13
• 2.0.14
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• 2.0.21
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• 2.0.24
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• 2.0.27
• 2.0.28
• 2.0.29
• 2.0.30
• 2.0.31
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• 2.0.33
• 2.0.34
• 2.0.35
• 2.0.36
• 2.0.37
• 2.0.38
• 2.0.39
• 2.0.40
• 2.0.41
• 2.0.42
• 2.0.43
• 2.0.44
• 2.0.45
• 2.0.46
• 2.0.47
• 2.0.48
• 2.0.49
• 2.0.50
• 2.0.51
• 2.0.52
• 2.0.53
• 2.0.54
• 3.0.0
• 3.0.1
• 3.0.2
• 3.0.3
• 3.0.4
• 3.0.5
• 3.0.6
• 3.0.7
• 3.0.8
• 3.0.9
• 3.0.10
• 3.0.11
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• 3.0.16
• 3.0.17
• 3.0.18
• 3.0.19
• 3.0.20
• 3.0.21
• 3.0.22
• 3.0.23
• 3.0.24
• 3.0.25
• 3.0.26
• 3.0.27
• 3.0.28
• 3.0.29
• 3.0.30
• 3.0.31
• 3.0.32
• 3.0.33
• 3.0.34
• 3.0.35
• 3.0.36
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• 3.0.38
• 3.0.39
• 3.0.40
• 3.0.41
• 3.0.42
• 3.0.43
• 3.0.44
• 3.0.45
• 3.0.46
• 3.0.47
• 3.0.48
• 3.0.49
• 3.0.50
• 3.0.51
• 3.0.52
• 3.0.53

Website

• Product: https://github.com/phpseclib/phpseclib/

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