High

CVE-2026-20293 — Cisco UCS and UCS-Based Appliances UEFI Shell Secure Boot Bypass Vulnerability

A vulnerability in the Unified Extensible Firmware Interface (UEFI) Shell implementation of Cisco UCS Servers and UCS-based appliances could allow an authenticated attacker with valid credentials for a user account with the role of user or admin or an unauthenticated attacker with physical access to an affected device to bypass UEFI Secure Boot validation checks and execute unauthorized software. This vulnerability is due to the availability of memory write commands in the UEFI Shell while UEFI Secure Boot is enabled on a device. An attacker could exploit this vulnerability by selecting the UEFI Shell boot option at boot time and using available shell commands to modify UEFI memory variables. A successful exploit could allow the attacker to manipulate the preboot environment, overwrite UEFI Secure Boot-related memory values, and execute unauthorized software on the affected device.

Published Sep 8, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: cisco

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Cisco

Cisco Unified Computing System (Managed) and 3 more

CVSS base

7.1

High · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Cisco Cisco Unified Computing System (Managed), Cisco Cisco Unified Computing System (Standalone), Cisco Cisco Unified Computing System E-Series Software (UCSE)…).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Cisco	Cisco Unified Computing System (Managed)	version 4.1(3k)version 4.0(4o)version 4.2(2e)version 4.2(3d)version 4.2(3e)version 4.2(3g)version 4.1(3l)version 4.3(2b) and 93 more version 4.2(3h)version 4.2(3i)version 4.3(2c)version 4.1(3m)version 4.3(2e)version 4.3(3a)version 4.2(3j)version 4.3(3c)version 4.3(4a)version 4.2(3k)version 4.3(4b)version 4.3(4c)version 4.2(3l)version 4.3(4d)version 4.2(3m)version 4.3(2f)version 4.3(5a)version 4.3(4e)version 4.1(3n)version 4.3(4f)version 4.2(3n)version 4.3(5c)version 4.2(3o)version 4.3(5d)version 4.3(6a)version 4.3(6b)version 4.3(5e)version 4.3(6c)version 6.0(1b)version 4.2(3p)version 6.0(1c)version 4.3(6d)version 6.0(1d)version 6.0(1e)version 4.3(6e)version 6.0(1f)version 4.3(6f)version 6.0(2b)version 6.0(1h)version 4.2(3r)version 6.0(2c)version 4.3(6g)version 4.0(1a)version 4.1(1a)version 4.1(1b)version 4.0(4h)version 4.1(1c)version 4.0(4e)version 4.0(4g)version 4.0(2e)version 4.0(4a)version 4.0(2d)version 4.0(1b)version 4.0(4f)version 4.0(4c)version 4.0(1c)version 4.0(4b)version 4.0(2b)version 4.0(4d)version 4.0(2a)version 4.0(1d)version 4.0(4i)version 4.1(1d)version 4.1(2a)version 4.1(1e)version 4.1(2b)version 4.0(4k)version 4.1(3a)version 4.1(3b)version 4.1(2c)version 4.0(4l)version 4.1(4a)version 4.1(3c)version 4.1(3d)version 4.2(1c)version 4.2(1d)version 4.0(4m)version 4.1(3e)version 4.2(1f)version 4.1(3f)version 4.2(1i)version 4.2(1k)version 4.0(4n)version 4.1(3h)version 4.2(1l)version 4.2(1m)version 4.1(3i)version 4.2(2a)version 4.2(1n)version 4.1(3j)version 4.2(2c)version 4.2(2d)version 4.2(3b)	Vulnerable	CVE Program (cve.org) e CISA ADP
Cisco	Cisco Unified Computing System (Standalone)	version 4.0(2g)version 3.1(2i)version 3.1(1d)version 4.0(4i)version 4.1(1c)version 4.0(2c)version 4.0(1e)version 4.0(2h) and 172 more version 4.0(4h)version 4.0(1h)version 4.0(2l)version 3.1(3g)version 4.0(1.240)version 4.0(2f)version 4.0(1g)version 4.0(2i)version 3.1(3i)version 4.0(4d)version 4.1(1d)version 3.1(3c)version 4.0(4k)version 3.1(2d)version 3.1(3a)version 3.1(3j)version 4.0(2d)version 4.1(1f)version 4.0(4j)version 4.0(2m)version 4.0(2k)version 4.0(1c)version 4.0(4f)version 4.0(4c)version 3.1(3d)version 3.1(2g)version 3.1(2c)version 4.0(1d)version 3.1(2e)version 4.0(1a)version 4.0(1b)version 3.1(3b)version 4.0(4b)version 3.1(2b)version 4.0(4e)version 3.1(3h)version 4.0(4l)version 4.1(1g)version 4.1(2a)version 4.0(2n)version 4.1(1h)version 3.1(3k)version 4.1(2b)version 4.0(2o)version 4.0(4m)version 4.1(2d)version 4.1(3b)version 4.0(2p)version 4.1(2e)version 4.1(2f)version 4.0(4n)version 4.0(2q)version 4.1(3c)version 4.0(2r)version 4.1(3d)version 4.1(2g)version 4.1(2h)version 4.1(3g)version 4.1(3f)version 4.1(2j)version 4.1(2k)version 4.1(3h)version 4.2(2a)version 4.1(3i)version 4.2(2f)version 4.2(2g)version 4.2(3b)version 4.1(3l)version 4.2(3d)version 4.3(1.230097)version 4.2(1e)version 4.2(1b)version 4.2(1j)version 4.2(1i)version 4.2(1f)version 4.2(1a)version 4.2(1c)version 4.2(1g)version 4.3(1.230124)version 4.1(2l)version 4.2(3e)version 4.3(1.230138)version 4.2(3g)version 4.3(2.230207)version 4.2(3h)version 4.2(3i)version 4.3(2.230270)version 4.1(3m)version 4.1(2m)version 4.3(2.240002)version 4.3(3.240022)version 4.2(3j)version 4.1(3n)version 4.3(2.240009)version 4.3(3.240041)version 4.2(3k)version 4.3(3.240043)version 4.3(4.240142)version 4.3(2.240037)version 4.3(2.240053)version 4.3(4.240152)version 4.2(3l)version 4.3(2.240077)version 4.3(4.242028)version 4.3(4.241063)version 4.3(4.242038)version 4.2(3m)version 4.3(2.240090)version 4.3(5.240021)version 4.3(2.240107)version 4.3(4.242066)version 4.2(3n)version 4.3(5.250001)version 4.2(3o)version 4.3(2.250016)version 4.3(2.250021)version 4.3(5.250030)version 4.3(2.250022)version 4.3(6.250039)version 4.3(6.250040)version 4.3(5.250033)version 4.3(6.250044)version 4.3(6.250053)version 4.3(2.250037)version 4.3(2.250045)version 4.3(4.252001)version 4.3(4.252002)version 6.0(1.250127)version 4.2(3p)version 6.0(1.250131)version 4.3(6.250101)version 6.0(1.250174)version 4.3(6.250117)version 4.3(5.250043)version 4.3(5.250045)version 4.3(6.250060)version 6.0(1.250130)version 4.3(4.241014)version 6.0(1.251030)version 4.3(2.250063)version 6.0(1.250192)version 4.3(6.260003)version 6.0(1.250194)version 6.0(1.260001)version 4.3(6.260017)version 4.3(2.260007)version 6.0(2.260044)version 6.0(2.260042)version 4.0(1.260003)version 2.0(2.260062)version 2.0(1.250127)version 2.0(1.250096)version 4.0(1.260004)version 6.0(2.260026)version 6.0(1.251006)version 1.2(0.250011)version 1.1(0.250016)version 1.0(0.240001)version 1.0(0.250003)version 1.2(0.250013)version 1.1(0.250026)version 1.0(1.250002)version 1.1(0.250022)version 1.1(0.250025)version 1.0(1.250032)version 6.0(2.260034)version 6.0(2.260069)version 4.3(6.260033)version 2.0(2.260101)version 4.2(3q)version 4.2(3r)version 1.2(0.260005)	Vulnerable	CVE Program (cve.org) e CISA ADP
Cisco	Cisco Unified Computing System E-Series Software (UCSE)	version 4.11.1version 4.12.1version 4.12.2version 4.15.2version 4.15.3version 4.15.4	Vulnerable	CVE Program (cve.org) e CISA ADP
Cisco	Enterprise Nfv Infrastructure Software	version 4.1.1version 3.9.1version 3.5.2version 3.12.2version 3.6.2version 3.9.2version 3.11.3version 3.11.1 and 5 more version 3.5.1version 3.3.1version 3.10.2version 3.12.1bversion 3.4.1	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Local

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
7.1	CVSS 3.1	High	1.8	5.2	psirt@cisco.com via NIST National Vulnerability Database
7.1	CVSS 3.1	High	—	—	cisco via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N (score shown at the top: psirt@cisco.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-749

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.

endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

2026
Affected products added · cisco/cisco enterprise nfv infrastructure software, cisco/cisco unified computing system (managed), cisco/cisco unified
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 15, 2026
CVSS changed · 7.1
Oct 15, 2026 · NIST National Vulnerability Database
Source status changed · → Awaiting Analysis
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Sep 8, 2026 · cisco

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

1 on the record

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ucs-uefi-sb-by
NIST National Vulnerability Database

Elsewhere on this site

Cisco
every CVE for this vendor

CWE-749
other pages naming this weakness

Related CVEs (same products)

Critical CVE-2026-76471 Cisco NX-OS Software NX-API Remote Code Execution Vulnerability 8d
High CVE-2026-76458 Cisco NX-OS Software Security Hardening Release: October 2026 - Improper Handling of Exceptional Conditions Vulnerabilities 8d
High CVE-2026-76457 Cisco NX-OS Software Security Hardening Release: October 2026 - Out-of-bounds Read Vulnerabilities 8d
Critical CVE-2026-76459 Cisco NX-OS Software Security Hardening Release: October 2026 - Out-of-bounds Write Vulnerabilities 8d
High CVE-2026-76453 Cisco NX-OS Software Security Hardening Release: October 2026 - Improper Neutralization Vulnerabilities 8d
High CVE-2026-76456 Cisco NX-OS Software Security Hardening Release: October 2026 - Improper Input Validation Vulnerabilities 8d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No FIRST EPSS score.
No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-20293 is "Cisco UCS and UCS-Based Appliances UEFI Shell Secure Boot Bypass Vulnerability", rated High. It affects Cisco Unified Computing System (Managed) (Cisco); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.1 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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