Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software WebVPN Denial of Service Vulnerability
A vulnerability in the WebVPN login process of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause increased CPU utilization on an affected device. The vulnerability is due to excessive processing load for existing WebVPN login operations. An attacker could exploit this vulnerability by sending multiple WebVPN login requests to the device. A successful exploit could allow the attacker to increase CPU load on the device, resulting in a denial of service (DoS) condition.
- Published
- May 3, 2019
- Updated
- Aug 11, 2026
- EPSS
- 2.0% · 80th percentile
- CWE
- CWE-400
Sign in to follow · You’ll be notified if a followed record enters KEV, gets an exploit or is updated.
Report tools
Action score
35
Monitor
Low priority for now.
- CVSS
- 34 / 40 · 8.6 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 1 / 30 · 2.0%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 8.6
- CNA · cisco
- 8.6
- agree
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpAffected systems
| Vendor | Product | CPE |
|---|---|---|
| cisco | adaptive security appliance software | cpe:2.3:a:cisco:adaptive_security_appliance_software |
| cisco | asa 5505 | cpe:2.3:h:cisco:asa_5505 |
| cisco | asa 5510 | cpe:2.3:h:cisco:asa_5510 |
| cisco | asa 5512-x | cpe:2.3:h:cisco:asa_5512-x |
| cisco | asa 5515-x | cpe:2.3:h:cisco:asa_5515-x |
| cisco | asa 5520 | cpe:2.3:h:cisco:asa_5520 |
| cisco | asa 5525-x | cpe:2.3:h:cisco:asa_5525-x |
| cisco | asa 5540 | cpe:2.3:h:cisco:asa_5540 |
| cisco | asa 5545-x | cpe:2.3:h:cisco:asa_5545-x |
| cisco | asa 5550 | cpe:2.3:h:cisco:asa_5550 |
| cisco | asa 5555-x | cpe:2.3:h:cisco:asa_5555-x |
| cisco | asa 5580 | cpe:2.3:h:cisco:asa_5580 |
and 2 more
Using adaptive security appliance software? Add it to your stack and be the first to know about CVEs like this one. (Firewall)
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- cisco adaptive security appliance softwarebefore 9.4.4.34
- cisco adaptive security appliance software9.5 and later · before 9.6.4.25
- cisco adaptive security appliance software9.7 and later · before 9.8.4
- cisco adaptive security appliance software9.9 and later · before 9.9.2.50
Versions reported by the vendor
Affected version ranges reported by the assigning authority (cisco). Independent of NVD's CPE analysis and usually ahead of it.
Cisco Cisco Adaptive Security Appliance (ASA) Software
- unspecified and later · before 9.4.4.34affected
- unspecified and later · before 9.6.4.25affected
- unspecified and later · before 9.8.4affected
- unspecified and later · before 9.9.2.50affected
Same product
cisco: all recordsOther highest-scoring records for the same primary product.
- CVE-2025-20362Update: On November 5, 2025, Cisco became aware of a new attack variant against devices running Cisco Secure ASA Software or Cisco Secure FTKEV90Now
- CVE-2025-20333A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat DKEV90Now
- CVE-2020-3452Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Web Services Read-Only Path Traversal VulnerabilityKEV90Now
- CVE-2018-0296A vulnerability in the web interface of the Cisco Adaptive Security Appliance (ASA) could allow an unauthenticated, remote attacker to causeKEV90Now
- CVE-2024-20353A vulnerability in the management and VPN web servers for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat DefensKEV85Now
- CVE-2023-20269A vulnerability in the remote access VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTDKEV74This week
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
No fix version is recorded for this entry. Check the references for vendor advisories.
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-19-049 · May 1, 2019(Cisco Güvenlik Güncellemesi Yayınladı)
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
Impact can extend beyond the vulnerable component (scope changes).
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
CWE-400 · Uncontrolled Resource ConsumptionCVSS vector
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
nvd-primary
Root cause
Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.
The bug in code
The whole CWE-400 classA representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.
Vulnerable
function expand(node) { return node.children.map(expand);}Fixed
const MAX_DEPTH = 32;function expand(node, depth = 0) { if (depth > MAX_DEPTH) throw new Error("too deep"); return node.children.map((c) => expand(c, depth + 1));}Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Change log
No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.
References
Vendor advisories and official records. Exploit/PoC links are deliberately left out.