Medium Cross-site scripting

CVE-2026-20091 — Cisco UCS Manager and FXOS Software Stored Cross-Site Scripting Vulnerability

A vulnerability in the web-based management interface of Cisco FXOS Software and Cisco UCS Manager Software could allow an authenticated, remote attacker to conduct a stored cross-site scripting (XSS) attack against a user of the interface. This vulnerability is due to insufficient validation of user-supplied input by the web-based management interface of an affected system. An attacker could exploit this vulnerability by injecting malicious data into specific pages of the interface. A successful exploit could allow the attacker to execute arbitrary script code in the context of the affected interface or access sensitive, browser-based information. To exploit this vulnerability, the attacker must have valid credentials for a user account with the role of Administrator or AAA Administrator. 

Published Feb 25, 2026 · Updated Oct 13, 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

EPSS 0.2% (30-day exploitation probability)+1
Technical severity (medium)+3

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

0.18%

ahead of 7% of scored CVEs · Oct 14, 2026

Affects

Cisco

Cisco Firepower Extensible Operating System (FXOS) and 2 more

CVSS base

4.8

Medium · 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

Partial

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 Firepower Extensible Operating System (FXOS), Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, Cisco Cisco Unified Computing System (Managed)).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Exploitation requires user interaction: tighten email/web filtering and warn affected users.
Search available logs for exploit probes matching the vulnerability class (cross-site scripting), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Cisco	Cisco Firepower Extensible Operating System (FXOS)	version 2.14.1.131version 2.14.1.143version 2.14.1.163version 2.14.1.167version 2.16.0.128	Vulnerable	CVE Program (cve.org) e CISA ADP
Cisco	Cisco Secure Firewall Adaptive Security Appliance (ASA) Software	version 9.16.4.67version 9.18.4.40version 9.16.4.71version 9.20.3.4version 9.18.4.47version 9.20.3.7version 9.17.1.45version 9.19.1.37 and 125 more version 9.16.4.76version 9.18.4.50version 9.20.3.10version 9.18.4.52version 9.20.3.13version 9.18.4.53version 9.16.4.82version 9.20.3.16version 9.19.1.42version 9.18.4.57version 9.16.4.84version 9.20.3.20version 9.12.2version 9.12.1version 9.12.3version 9.12.4version 9.12.3.2version 9.12.3.12version 9.12.2.5version 9.12.1.2version 9.12.2.1version 9.12.3.7version 9.12.2.9version 9.12.3.9version 9.12.1.3version 9.12.4.2version 9.12.4.4version 9.12.4.7version 9.12.4.8version 9.12.4.10version 9.12.4.13version 9.12.4.18version 9.12.4.24version 9.16.1version 9.12.4.26version 9.16.1.28version 9.12.4.29version 9.16.2version 9.12.4.30version 9.16.2.3version 9.12.4.35version 9.16.2.7version 9.12.4.37version 9.17.1version 9.16.2.11version 9.16.2.13version 9.12.4.39version 9.12.4.38version 9.16.2.14version 9.17.1.7version 9.12.4.40version 9.16.3.3version 9.16.3version 9.17.1.9version 9.16.3.14version 9.12.4.41version 9.17.1.10version 9.18.1version 9.12.4.47version 9.16.3.15version 9.18.1.3version 9.17.1.11version 9.12.4.48version 9.18.2version 9.16.3.19version 9.17.1.13version 9.12.4.50version 9.17.1.15version 9.12.4.52version 9.16.3.23version 9.18.2.5version 9.16.4version 9.12.4.54version 9.17.1.20version 9.18.2.7version 9.19.1version 9.16.4.9version 9.12.4.55version 9.18.2.8version 9.16.4.14version 9.18.3version 9.19.1.5version 9.12.4.56version 9.17.1.30version 9.19.1.9version 9.18.3.39version 9.16.4.19version 9.12.4.58version 9.19.1.12version 9.18.3.46version 9.16.4.27version 9.19.1.18version 9.18.3.53version 9.18.3.55version 9.16.4.38version 9.17.1.33version 9.12.4.62version 9.16.4.39version 9.18.3.56version 9.16.4.42version 9.19.1.22version 9.18.4version 9.18.4.5version 9.19.1.24version 9.16.4.48version 9.18.4.8version 9.20.2version 9.19.1.27version 9.12.4.65version 9.16.4.55version 9.18.4.22version 9.20.2.10version 9.16.4.57version 9.19.1.28version 9.17.1.39version 9.12.4.67version 9.18.4.24version 9.20.2.21version 9.16.4.61version 9.19.1.31version 9.18.4.29version 9.20.2.22version 9.16.4.62version 9.18.4.34version 9.20.3	Vulnerable	CVE Program (cve.org) e CISA ADP
Cisco	Cisco Unified Computing System (Managed)	version 4.0(4h)version 4.1(1a)version 4.0(1c)version 4.0(4a)version 4.0(1a)version 4.0(1d)version 4.1(1c)version 4.0(2a) and 77 more version 4.0(4g)version 4.0(2e)version 4.0(4c)version 4.0(4f)version 4.0(1b)version 4.0(2b)version 4.0(2d)version 4.1(1b)version 4.0(4d)version 4.0(4e)version 4.0(4b)version 4.1(2a)version 4.1(1d)version 4.0(4i)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 4.1(3h)version 4.2(1k)version 4.2(1l)version 4.0(4n)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)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)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 4.3(2f)version 4.2(3m)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(5e)version 4.2(3p)	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

Network

Attack complexity

Low

Privileges required

High

User interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

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
4.8	CVSS 3.1	Medium	1.7	2.7	psirt@cisco.com via NIST National Vulnerability Database
4.8	CVSS 3.1	Medium	—	—	cisco via CVE Program (cve.org) e CISA ADP

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

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-79 · Cross-site Scripting (XSS)

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.18%

Detection

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

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Monitor CSP violation reports and script payloads in reflected parameters.

web/proxy/WAF logsnetwork IDS/IPSapplication logs

Timeline

What happened to this CVE, newest first.

2026
Affected products added · cisco/cisco firepower extensible operating system (fxos), cisco/cisco secure firewall adaptive security appliance (asa)
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 4.8
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Deferred
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Feb 25, 2026 · cisco

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ucsfxosxss-7sk
NIST National Vulnerability Database

Elsewhere on this site

Cisco
every CVE for this vendor

Cross-site scripting
same class

CWE-79
other pages naming this weakness

Related CVEs (same products)

Critical CVE-2026-76471 Cisco NX-OS Software NX-API Remote Code Execution Vulnerability 8d
Critical CVE-2026-76459 Cisco NX-OS Software Security Hardening Release: October 2026 - Out-of-bounds Write Vulnerabilities 8d
High CVE-2026-76457 Cisco NX-OS Software Security Hardening Release: October 2026 - Out-of-bounds Read Vulnerabilities 8d
High CVE-2026-76458 Cisco NX-OS Software Security Hardening Release: October 2026 - Improper Handling of Exceptional Conditions Vulnerabilities 8d
Critical CVE-2026-76455 Cisco NX-OS Software Security Hardening Release: October 2026 - Improper Access Control Vulnerabilities 8d
High CVE-2026-76453 Cisco NX-OS Software Security Hardening Release: October 2026 - Improper Neutralization 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 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-2026-20091 is "Cisco UCS Manager and FXOS Software Stored Cross-Site Scripting Vulnerability", rated Medium. It affects Cisco Firepower Extensible Operating System (FXOS) (Cisco); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 4.8 describes technical severity. EPSS 0.18% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

Comments

Moderated technical discussion. Read the community guidelines.

No comments yet.