Threats / Cisco / CVE-2020-3580
CVE-2020-3580
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Cisco Adaptive Security Appliance (ASA) and Firepower Threat vulnerability
Cisco ASA and FTD web interface contains insufficient input validation allowing cross-site scripting (XSS) attacks that could expose sensitive information or compromise administrator sessions.
Verdict
Today item, not a backlog item.
A reflected or stored XSS vulnerability in the web management interface of Cisco ASA/FTD enables attackers to inject malicious scripts. With high EPSS and active exploitation, this poses significant risk to firewall administrators and network security posture.
CISA KEV Yes · 2021-11-035Ransomware use Flagged5EPSS 0.85576 (verify live)6Exploit Public PoC7CVSS 6.13CISA SSVC Exploitation: active · Automatable: no · Impact: partial4
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Public proof-of-concept exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
396 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.85576 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 6.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N) · Affected: Cisco, Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD). Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
Weakness (CWE)
Mapped to CWE-79 Cross-site Scripting (XSS) — weakness family: Web / client.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 378 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
Public exploit available
Public exploit tooling is catalogued for this CVE (a public proof-of-concept / detection template). Catalog entries: nuclei template. We link the catalog page(s) only — no payload or code is hosted or restated here.Link, never host — the catalog page is the source; basicsecurity.net does not redistribute payloads.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious URL or inject script payload into the ASA/FTD web interface input fields.
Business
Attackers gain ability to execute arbitrary JavaScript in administrator browsers, risking credential theft and unauthorized firewall reconfiguration.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I execute the XSS payload to steal session cookies or authentication tokens from logged-in administrators.
Business
Compromise of admin credentials enables lateral movement into protected networks and potential deployment of ransomware or persistent backdoors.
3
Lateral reach — past segmentation narrative 3
Attacker
I use the compromised firewall access to modify security policies, disable logging, or establish command-and-control channels.
Business
Loss of perimeter security control, undetected data exfiltration, and inability to respond to or investigate security incidents.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05