CVE-2026-20135

HIGHPre-NVD 8.68.6—
EchelonGraph scoreHIGH confidence

Score 8.6 from GitHub Security Advisory (severity: HIGH) published 2026-09-16. a secondary CVSS source baseline 8.6; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
8.6EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.6Exploit: 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 TLS 1.3 implementation in Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to improper buffer management during the TLS 1.3 connection. An attacker could exploit this vulnerability by sending a crafted TLS 1.3 packet to an affected system through a TLS 1.3-enabled listening socket. A successful exploit could allow the attacker to cause the LINA process to crash, which would cause the device to reload. The reload can happen before or after authentication of the connection.Note: TLS 1.3 connections include both data traffic and user-management traffic.

CVSS v3
8.6
EG Score
8.6(high)
EG Risk
54(Track)
EG Risk 54/100SSVC: 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
Severity86% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
39%
KEV
Not listed

Published

September 16, 2026

Last Modified

September 18, 2026

Advisory Details (1)

Auto-updated Sep 16, 2026
No patch confirmed yet.
generic

Cisco Secure Firewall Threat Defense Software TLS 1.3 Denial of Service Vulnerability

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-tls1.3-dos-dLxwFWgF

Vendor Advisories for CVE-2026-20135(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 17× in last 7d / 17× 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 12:33 UTCGHSA enrichment
  2. 2026-09-19 01:07 UTCEG score recompute
  3. 2026-09-19 01:07 UTCGHSA enrichment
  4. 2026-09-18 19:27 UTCEPSS rescore
  5. 2026-09-18 13:41 UTCGHSA enrichment
  6. 2026-09-18 13:17 UTCGHSA enrichment
  7. 2026-09-18 01:51 UTCEG score recompute
  8. 2026-09-18 01:51 UTCGHSA enrichment
  9. 2026-09-17 14:25 UTCEG score recompute
  10. 2026-09-17 14:25 UTCGHSA enrichment
  11. 2026-09-17 13:52 UTCEG score recompute
  12. 2026-09-17 13:52 UTCGHSA enrichment
  13. 2026-09-17 08:54 UTCEG score recompute
  14. 2026-09-17 08:53 UTCGHSA enrichment
  15. 2026-09-16 21:27 UTCEG score recompute
  16. 2026-09-16 20:41 UTCEG score recompute
  17. 2026-09-16 20:29 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-20135?
CVE-2026-20135 is a high vulnerability published on September 16, 2026. A vulnerability in the TLS 1.3 implementation in Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to improper buffer…
When was CVE-2026-20135 disclosed?
CVE-2026-20135 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-2026-20135 actively exploited?
CVE-2026-20135 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 61.1% of all scored CVEs.
What is the CVSS score of CVE-2026-20135?
CVE-2026-20135 has a CVSS v3 base score of 8.6 (NVD).
How do I remediate CVE-2026-20135?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-20135, 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

Explore the affected products and dependency analysis for CVE-2026-20135

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