A vulnerability in the endpoint group (EPG) contract functionality of Cisco Nexus 9000 Series Fabric Switches in ACI Mode could allow an unauthenticated, remote attacker to bypass configured EPG contracts. This vulnerability is due to an improper control with EPG contracts. An attacker could exploit this vulnerability by sending IPv4 or IPv6 packets using UDP source and destination ports that are assigned to DHCP traffic through an affected device. A successful exploit could allow the attacker to bypass EPG contracts on the affected device.
CVE-2026-20038
MEDIUMPre-NVD 5.85.8Trending — 4 sources updated this week
EchelonGraph scoreHIGH confidence
“—” beside the score: it is equal to the CVSS score beside it.
Score 5.8 from GitHub Security Advisory published 2026-10-07. A secondary CVSS source baseline 5.8; sources differ by 0.0.
Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
5.8EG
EchelonGraph verdictMonitorRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.8Exploit: None knownExposed services: Not assessed
No fix is confirmed yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for the fix.
- CVSS v3
- 5.8
- EG Score
- 5.8MEDIUMhigh confidence
- EG Risk
- 41EG Risk 41/100
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 (value × EchelonGraph’s weight)Severity58% × 45%The EG Score, 5.8 of 10.Exploitation0.3% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability100% × 15%CISA's SSVC Automatable value: yes (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix. - EPSS PROB
- 0.3%
- EPSS %ILE
- 21st
- KEV
- Not listed
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
October 7, 2026
Last Modified
October 8, 2026
Advisory Details (1)
Auto-updated Oct 7, 2026No fix on record yet.
Web page
Cisco Nexus 9000 Series Fabric Switches in ACI Mode Endpoint Group Contract Bypass Vulnerability
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-aci-epgcbp-SfDU7NLfVendor Advisories for CVE-2026-20038(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 23× in last 7d / 23× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
- 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-12 16:24 UTCEG score recompute
- 2026-10-11 20:06 UTCEG score recompute
- 2026-10-11 17:56 UTCGHSA enrichmentGHSA-8r87-mj76-xw8h · GitHub CVSS 5.8
- 2026-10-11 17:19 UTCEG score recompute
- 2026-10-11 14:51 UTCEG score recompute
- 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-10 19:59 UTCEPSS rescoreEPSS 0.3% · 21st percentile
- 2026-10-10 18:27 UTCEG score recompute
- 2026-10-10 18:27 UTCGHSA enrichmentGHSA-8r87-mj76-xw8h · GitHub CVSS 5.8
- 2026-10-09 20:06 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-10-09 19:23 UTCGHSA enrichmentGHSA-8r87-mj76-xw8h · GitHub CVSS 5.8
- 2026-10-08 20:21 UTCGHSA enrichmentGHSA-8r87-mj76-xw8h · GitHub CVSS 5.8
- 2026-10-08 18:31 UTCEG score recompute
- 2026-10-08 18:31 UTCGHSA enrichmentGHSA-8r87-mj76-xw8h · GitHub CVSS 5.8
- 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-10-07 19:20 UTCEG score recompute
- 2026-10-07 19:20 UTCGHSA enrichmentGHSA-8r87-mj76-xw8h · GitHub CVSS 5.8
- 2026-10-07 18:28 UTCEG score recompute
- 2026-10-07 17:37 UTCEG score recompute
- 2026-10-07 16:36 UTCEG score recomputeFirst assessed: 5.8 MEDIUM
- 2026-10-07 16:31 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2026-20038?
CVE-2026-20038 is a medium-severity vulnerability; its CVE record was published on October 7, 2026. A vulnerability in the endpoint group (EPG) contract functionality of Cisco Nexus 9000 Series Fabric Switches in ACI Mode could allow an unauthenticated, remote attacker to bypass configured EPG contracts. This vulnerability is due to an improper control with EPG contracts. An attacker could…
When was the CVE record for CVE-2026-20038 published?
The CVE record for CVE-2026-20038 was published on October 7, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 8, 2026; the record at its source may have been updated since.
Is CVE-2026-20038 actively exploited?
CVE-2026-20038 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (21st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-20038?
CVE-2026-20038 has a CVSS base score of 5.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-20038?
No fix for CVE-2026-20038 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-20038 are linked in the Vendor Advisories panel on this page.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-20038
Is Your Infrastructure Affected by CVE-2026-20038?
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