CVE-2026-55599
phpseclib: X.509 certificate validation sends attacker-controlled outbound requests (server-side request forgery) via Authority Information Access
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.
INFO
Published Date :
June 22, 2026, 9:16 p.m.
Last Modified :
June 26, 2026, 8:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update phpseclib to version 1.0.30 or later.
- Update phpseclib to version 2.0.55 or later.
- Update phpseclib to version 3.0.54 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-55599.
| URL | Resource |
|---|---|
| https://github.com/phpseclib/phpseclib/security/advisories/GHSA-m557-wrgg-6rp4 | Exploit Mitigation Vendor Advisory |
| https://github.com/phpseclib/phpseclib/security/advisories/GHSA-m557-wrgg-6rp4 | Exploit Mitigation Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-55599 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-55599
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-55599 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-55599 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jun. 26, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:phpseclib:phpseclib:*:*:*:*:*:*:*:* versions from (including) 0.1.1 up to (excluding) 1.0.30 *cpe:2.3:a:phpseclib:phpseclib:*:*:*:*:*:*:*:* versions from (including) 2.0.0 up to (excluding) 2.0.55 *cpe:2.3:a:phpseclib:phpseclib:*:*:*:*:*:*:*:* versions from (including) 3.0.0 up to (excluding) 3.0.54 Added Reference Type GitHub, Inc.: https://github.com/phpseclib/phpseclib/security/advisories/GHSA-m557-wrgg-6rp4 Types: Exploit, Mitigation, Vendor Advisory Added Reference Type CISA-ADP: https://github.com/phpseclib/phpseclib/security/advisories/GHSA-m557-wrgg-6rp4 Types: Exploit, Mitigation, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 23, 2026
Action Type Old Value New Value Added Reference https://github.com/phpseclib/phpseclib/security/advisories/GHSA-m557-wrgg-6rp4 Added SSVC {'id': 'CVE-2026-55599', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-23T14:12:41.401298Z'} -
New CVE Received by [email protected]
Jun. 22, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'phpseclib', 'product': 'phpseclib', 'versions': [{'status': 'affected', 'version': '>= 0.1.1, < 1.0.30'}, {'status': 'affected', 'version': '>= 2.0.0, < 2.0.55'}, {'status': 'affected', 'version': '>= 3.0.0, < 3.0.54'}]}] Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N Added CWE CWE-918 Added Reference https://github.com/phpseclib/phpseclib/security/advisories/GHSA-m557-wrgg-6rp4