CVE-2026-55599

MEDIUMPre-NVD 5.85.8—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1%, top 97% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
5.8
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
5.8
EG Score
5.8(medium)
EPSS
3.2%
KEV
Not listed

Published

June 22, 2026

Last Modified

June 26, 2026

Advisory Details (1)

Auto-updated Jun 23, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

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

https://github.com/phpseclib/phpseclib/security/advisories/GHSA-m557-wrgg-6rp4

Vendor Advisories for CVE-2026-55599(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
Packagist(1)
PackageVulnerable rangeFixed inDependents
phpseclib/phpseclib0.3.0 ... 1.0.9 (38 versions)1.0.30—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 19× in last 7d / 52× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-14 03:58 UTCEG score recompute
  2. 2026-07-13 22:31 UTCEPSS rescore
  3. 2026-07-13 06:13 UTCEPSS rescore
  4. 2026-07-13 06:13 UTCEPSS rescore
  5. 2026-07-13 03:43 UTCEG score recompute
  6. 2026-07-12 05:46 UTCEPSS rescore
  7. 2026-07-12 03:27 UTCEG score recompute
  8. 2026-07-11 08:27 UTCEPSS rescore
  9. 2026-07-11 08:27 UTCEPSS rescore
  10. 2026-07-11 03:11 UTCEG score recompute
  11. 2026-07-10 02:51 UTCEG score recompute
  12. 2026-07-09 19:10 UTCEPSS rescore
  13. 2026-07-09 19:10 UTCEPSS rescore
  14. 2026-07-09 02:21 UTCEG score recompute
  15. 2026-07-08 15:16 UTCEPSS rescore
  16. 2026-07-08 15:16 UTCEPSS rescore
  17. 2026-07-08 02:04 UTCEG score recompute
  18. 2026-07-07 13:46 UTCEPSS rescore
  19. 2026-07-07 13:46 UTCEPSS rescore
  20. 2026-07-07 01:49 UTCEG score recompute
  21. 2026-07-06 16:27 UTCEPSS rescore
  22. 2026-07-06 16:27 UTCEPSS rescore
  23. 2026-07-06 02:23 UTCEPSS rescore
  24. 2026-07-06 02:23 UTCEPSS rescore
  25. 2026-07-06 01:32 UTCEG score recompute
Show 27 more
  1. 2026-07-05 01:17 UTCEG score recompute
  2. 2026-07-04 06:31 UTCEPSS rescore
  3. 2026-07-04 06:31 UTCEPSS rescore
  4. 2026-07-04 00:46 UTCEG score recompute
  5. 2026-07-03 00:16 UTCEG score recompute
  6. 2026-07-02 00:01 UTCEG score recompute
  7. 2026-06-30 23:46 UTCEG score recompute
  8. 2026-06-30 23:22 UTCEPSS rescore
  9. 2026-06-29 23:30 UTCEG score recompute
  10. 2026-06-29 14:06 UTCEPSS rescore
  11. 2026-06-29 14:06 UTCEPSS rescore
  12. 2026-06-28 23:14 UTCEG score recompute
  13. 2026-06-28 14:07 UTCEPSS rescore
  14. 2026-06-28 04:56 UTCEPSS rescore
  15. 2026-06-28 04:56 UTCEPSS rescore
  16. 2026-06-27 22:59 UTCEG score recompute
  17. 2026-06-27 03:08 UTCEPSS rescore
  18. 2026-06-26 22:43 UTCEG score recompute
  19. 2026-06-25 22:27 UTCEG score recompute
  20. 2026-06-25 13:49 UTCEPSS rescore
  21. 2026-06-24 22:11 UTCEG score recompute
  22. 2026-06-24 14:05 UTCEPSS rescore
  23. 2026-06-23 21:56 UTCEG score recompute
  24. 2026-06-23 21:33 UTCEPSS rescore
  25. 2026-06-23 21:33 UTCEPSS rescore
  26. 2026-06-22 21:38 UTCEG score recompute
  27. 2026-06-22 21:37 UTCNVD updatefirst tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55599?
CVE-2026-55599 is a medium vulnerability published on June 22, 2026. 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…
When was CVE-2026-55599 disclosed?
CVE-2026-55599 was first published in the National Vulnerability Database on June 22, 2026, with the most recent update on June 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55599 actively exploited?
CVE-2026-55599 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 3.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-55599?
CVE-2026-55599 has a CVSS v3 base score of 5.8 (NVD).
How do I remediate CVE-2026-55599?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55599, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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