CVE-2026-55599Public exploitNetwork attack vector

SSRF via unrestricted X.509 AIA URL fetching

Published Jun 22, 2026 · Updated Jun 22, 2026

SSRF in phpseclib before 1.0.30, 2.0.55, and 3.0.54 allows remote attackers to reach internal services via crafted X.509 certificates. X509::validateSignature() passes the certificate's unrestricted AIA caIssuers URL to fetchURL(), which opens a socket to the supplied host and port by default. Affected applications must validate attacker-influenced certificates; the blind fetch supports internal port scanning and HTTP GETs but does not expose response bodies directly.

CVSS severity5.8
Medium
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

SSRF in phpseclib before 1.0.30, 2.0.55, and 3.0.54 allows remote attackers to reach internal services via crafted X.509 certificates. X509::validateSignature() passes the certificate's unrestricted AIA caIssuers URL to fetchURL(), which opens a socket to the supplied host and port by default. Affected applications must validate attacker-influenced certificates; the blind fetch supports internal port scanning and HTTP GETs but does not expose response bodies directly.

The record

CVE
CVE-2026-55599
Published
Jun 22, 2026
Updated
Jun 22, 2026
Vendor
phpseclib
Product
phpseclib
Classifications
CWE-276, CWE-918, T1046
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 22, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 0.1.1, < 1.0.30
  2. Affected versionversion=>= 2.0.0, < 2.0.55
  3. Affected versionversion=>= 3.0.0, < 3.0.54

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

phpseclib · phpseclibversion=>= 0.1.1, < 1.0.30; version=>= 2.0.0, < 2.0.55; version=>= 3.0.0, < 3.0.54

Published CVSS scores

5.8GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-276Incorrect Default Permissions
CWE-918Server-Side Request Forgery (SSRF)
T1046Network Service Discovery

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo