CVE-2026-20242

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreHIGH confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-09-16. a secondary CVSS source baseline 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.8Exploit: None knownExposed: 0

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

A vulnerability in the External Database Access feature of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to execute arbitrary commands as root on an affected device. This vulnerability is due to insecure deserialization of a user-supplied Java byte stream from a host that is configured in the external database access list. An attacker could exploit this vulnerability by sending a crafted, serialized Java byte stream to a specific TCP port of an affected device. A successful exploit could allow the attacker to execute arbitrary commands on the device and elevate privileges to root. Notes: This vulnerability can be exploited only by an attacker who has control of a host in the external database access list. If the FMC management interface does not have public internet access, the attack surface that is associated with this vulnerability is reduced.

CVSS v3
9.8
EG Score
9.8(high)
EG Risk
59(Track)
EG Risk 59/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
49%
KEV
Not listed

Published

September 16, 2026

Last Modified

September 18, 2026

Advisory Details (1)

Auto-updated Sep 18, 2026
No patch confirmed yet.
generic

Cisco Secure Firewall Management Center Software Java Deserialization Remote Code Execution Vulnerability

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-javarce-y2NypXwk

Vendor Advisories for CVE-2026-20242(2)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 30× in last 7d / 30× 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. 2026-09-19 13:47 UTCGHSA enrichment
  2. 2026-09-19 09:40 UTCGHSA enrichment
  3. 2026-09-19 05:29 UTCGHSA enrichment
  4. 2026-09-19 01:21 UTCGHSA enrichment
  5. 2026-09-18 21:14 UTCEG score recompute
  6. 2026-09-18 21:14 UTCGHSA enrichment
  7. 2026-09-18 19:27 UTCEPSS rescore
  8. 2026-09-18 16:56 UTCGHSA enrichment
  9. 2026-09-18 12:49 UTCGHSA enrichment
  10. 2026-09-18 08:42 UTCGHSA enrichment
  11. 2026-09-18 04:34 UTCEG score recompute
  12. 2026-09-18 04:34 UTCGHSA enrichment
  13. 2026-09-18 04:04 UTCEG score recompute
  14. 2026-09-18 04:04 UTCGHSA enrichment
  15. 2026-09-18 03:51 UTCGHSA enrichment
  16. 2026-09-17 23:44 UTCGHSA enrichment
  17. 2026-09-17 19:32 UTCEG score recompute
  18. 2026-09-17 19:32 UTCGHSA enrichment
  19. 2026-09-17 15:24 UTCEG score recompute
  20. 2026-09-17 15:24 UTCGHSA enrichment
  21. 2026-09-17 15:04 UTCEG score recompute
  22. 2026-09-17 15:04 UTCGHSA enrichment
  23. 2026-09-17 13:29 UTCGHSA enrichment
  24. 2026-09-17 09:20 UTCGHSA enrichment
  25. 2026-09-17 05:13 UTCGHSA enrichment
Show 5 more
  1. 2026-09-17 01:06 UTCEG score recompute
  2. 2026-09-17 01:06 UTCGHSA enrichment
  3. 2026-09-16 20:30 UTCEG score recompute
  4. 2026-09-16 20:09 UTCEG score recompute
  5. 2026-09-16 20:09 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-20242?
CVE-2026-20242 is a critical vulnerability published on September 16, 2026. A vulnerability in the External Database Access feature of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to execute arbitrary commands as root on an affected device. This vulnerability is due to insecure deserialization of a…
When was CVE-2026-20242 disclosed?
CVE-2026-20242 was first published in the National Vulnerability Database on September 16, 2026, with the most recent update on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-20242 actively exploited?
CVE-2026-20242 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 50.8% of all scored CVEs.
What is the CVSS score of CVE-2026-20242?
CVE-2026-20242 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-20242?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-20242, 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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