# CVE-2026-55599: php-phpseclib: phpseclib is a PHP secure communications library

CVE-2026-55599 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-55599, released June 24, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-55599
- Priority: Routine
- CVSS: 5.8 (medium)
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 22, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | php-phpseclib Debian 14 | 2.0.55-1 | [DEBIAN-CVE-2026-55599](https://patchblox.com/security/data/fix/linux/debian-cve-2026-55599.md) | Jun 24, 2026 |
| Linux | php-phpseclib3 Debian 14 | 3.0.55-1 | [DEBIAN-CVE-2026-55599](https://patchblox.com/security/data/fix/linux/debian-cve-2026-55599.md) | Jun 24, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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