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Fencer Vulns
medium 5.8

CVE-2026-55599 json

phpseclib: X.509 certificate validation sends attacker-controlled outbound requests (server-side request forgery) via Authority Information Access

published 2026-06-16 4 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-38348 , GHSA-m557-wrgg-6rp4

cvss
5.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 11%
public exploits
0
none known

Summary

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.

Patch / fix

  • packagist phpseclib/phpseclib 1.0.30, 2.0.55, 3.0.54
  • phpseclib phpseclib 1.0.30, 2.0.55, 3.0.54
  • php-phpseclib Debian 14 2.0.55-1
  • php-phpseclib3 Debian 14 3.0.55-1

debian advisories DEBIAN-CVE-2026-55599

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/phpseclib/phpseclib/security/advisories/GHSA-m557-wrgg-6rp4 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
GitHub 3.1 5.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N

Affected packages

ecosystem package affected fixed in
packagist phpseclib/phpseclib
>=0.1.1, <1.0.30
>=2.0.0, <2.0.55
>=3.0.0, <3.0.54
1.0.30
2.0.55
3.0.54

Affected products

  • phpseclib phpseclib

Classification

Weakness
  • CWE-918 Server-Side Request Forgery

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.