A vulnerability in the bootloader of Cisco IOS XE Software for Cisco Catalyst 9200 Series Switches, Cisco Catalyst ESS9300 Embedded Series Switches, Cisco Catalyst IE9310 and IE9320 Rugged Series Switches, and Cisco IE3500 and IE3505 Rugged Series Switches could allow an authenticated, local attacker with level-15 privileges or an unauthenticated attacker with physical access to an affected device to execute arbitrary code at boot time and break the chain of trust. This vulnerability is due to insufficient validation of software at boot time. An attacker could exploit this vulnerability by manipulating the loaded binaries on an affected device to bypass some of the integrity checks that are performed during the boot process. A successful exploit could allow the attacker to execute code that bypasses the requirement to run Cisco-signed images. Cisco has assigned this security advisory a Security Impact Rating (SIR) of High rather than Medium as the score indicates because this vulnerability allows an attacker to bypass a major security feature of a device.
CVE-2026-20104
“—” beside the score: it is equal to the CVSS score beside it.
Score 6.1 from GitHub Security Advisory (severity: MODERATE) published 2026-03-25. A secondary CVSS source baseline 6.1; sources differ by 0.0.
Also known asEUVD-2026-15435 (ENISA EUVD) · GHSA-38h5-57rq-7mj8 (GitHub Security Advisories)Source: ENISA EUVD
- Lower severity and no public exploit yet
A fix is available — apply it.
- CVSS v3
- 6.1
- EG Score
- 6.1MEDIUMmedium confidence
- EG Risk
- 28EG Risk 28/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity61% × 45%Impact severity (EG Severity): CVSS 6.1 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation0.2% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability0% × 15%CISA's SSVC Automatable value: no (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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: A fix is available. Apply it within your standard update timelines. - EPSS PROB
- 0.2%
- EPSS %ILE
- 5th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (6.1): severity, escalated by confirmed exploitation. This CVE's 6.1 is its impact severity (EG Severity), not escalated.
- EG Severity
- 6.1 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (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
March 25, 2026
Last Modified
September 28, 2026
Advisory Details (1)
Auto-updated Aug 6, 2026Cisco IOS XE Software for Cisco Catalyst and Rugged Series Switches Secure Boot Bypass Vulnerability
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-xe-secureboot-bypass-B6uYxYSZVendor Advisories for CVE-2026-20104(1)
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 8× in last 7d / 32× 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 its CVE.org record (CNA or CISA ADP). 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). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.
Showing the most recent 100 of 126 rows on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 26 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-11-12 16:33 UTCEPSS rescoreEPSS 0.2% · 5th percentile
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- 2026-11-07 19:42 UTCGHSA enrichmentGHSA-38h5-57rq-7mj8 · GitHub severity MODERATE · GitHub CVSS 6.1
- 2026-11-07 19:42 UTCEchelonGraph re-scored
- 2026-11-07 16:38 UTCEPSS rescoreEPSS 0.2% · 5th percentile
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- 2026-10-25 14:44 UTCEchelonGraph re-scored
- 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.2% · 4th percentile
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- 2026-10-23 05:51 UTCEchelonGraph re-scored
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- 2026-10-23 05:51 UTCGHSA enrichmentGHSA-38h5-57rq-7mj8 · GitHub CVSS 6.1
- 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.2% · 4th percentile
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- 2026-10-18 03:57 UTCEchelonGraph re-scored
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- 2026-10-12 16:24 UTCEchelonGraph re-scored
- 2026-10-11 20:06 UTCEchelonGraph re-scored
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- 2026-10-11 14:51 UTCEchelonGraph re-scored
- 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.2% · 4th percentile
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- 2026-09-29 15:21 UTCEPSS rescoreEPSS 0.2% · 3rd percentile
- 2026-09-28 15:34 UTCEchelonGraph re-scored
- 2026-09-28 15:34 UTCGHSA enrichmentGHSA-38h5-57rq-7mj8 · GitHub CVSS 6.1
- 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.2% · 4th percentile
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- 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-16 10:22 UTCEchelonGraph re-scored
- 2026-08-16 10:22 UTCGHSA enrichmentGHSA-38h5-57rq-7mj8 · GitHub CVSS 6.1
- 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-14 06:42 UTCEchelonGraph re-scored
- 2026-08-14 06:42 UTCGHSA enrichmentGHSA-38h5-57rq-7mj8 · GitHub CVSS 6.1
- 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-12 20:57 UTCEchelonGraph re-scored
- 2026-08-12 20:57 UTCGHSA enrichmentGHSA-38h5-57rq-7mj8 · GitHub CVSS 6.1
- 2026-08-12 13:50 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-11 13:42 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-11 08:28 UTCEchelonGraph re-scored
- 2026-08-11 08:28 UTCGHSA enrichmentGHSA-38h5-57rq-7mj8 · GitHub CVSS 6.1
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Frequently asked(5)
What is CVE-2026-20104?
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Dependency Blast Radius
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