Cisco ASA and FTD Cross-Site Scripting (XSS)
CVE-2020-3580 is a medium-severity improper neutralization of input during web page generation vulnerability in Cisco Adaptive Security Appliance (ASA) Software from Cisco, with a CVSS 3.1 base score of 6.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. CISA added it to the Known Exploited Vulnerabilities catalogue on November 3, 2021, which means attacks have been observed in the wild, including in ransomware campaigns.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Secure Firewall Threat Defense to 6.4.0.12 or 6.6.4 or 6.7.0.2, whichever matches your release line, or a later version.
- Update Adaptive Security Appliance Software to 9.8.4.34 or 9.9.2.85 or 9.12.4.13 or 9.13.1.21, whichever matches your release line, or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on tools.cisco.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Cisco | Cisco Adaptive Security Appliance (ASA) Software | Not specified in the record | Not stated |
| Cisco | Secure Firewall Threat Defense | before 6.4.0.12; 6.5.0 up to, but not including, 6.6.4; 6.7.0 up to, but not including, 6.7.0.2 | 6.4.0.12, 6.6.4, 6.7.0.2 |
| Cisco | Adaptive Security Appliance Software | before 9.8.4.34; 9.9 up to, but not including, 9.9.2.85; 9.10 up to, but not including, 9.12.4.13; 9.13 up to, but not including, 9.13.1.21; 9.14 up to, but not including, 9.14.2.8; 9.15 up to, but not including, 9.15.1.15 | 9.8.4.34, 9.9.2.85, 9.12.4.13, 9.13.1.21, 9.14.2.8, 9.15.1.15 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- LowSome restricted data can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 6.1 | Medium | CNA (cisco.com) |
| CVSS 3.1 | 6.1 | Medium | NVD |
| CVSS 2.0 | 2.6 | Low | NVD |
Official description
Multiple vulnerabilities in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to conduct cross-site scripting (XSS) attacks against a user of the web services interface of an affected device. The vulnerabilities are due to insufficient validation of user-supplied input by the web services interface of an affected device. An attacker could exploit these vulnerabilities by persuading a user of the interface to click a crafted link. A successful exploit could allow the attacker to execute arbitrary script code in the context of the interface or allow the attacker to access sensitive, browser-based information. Note: These vulnerabilities affect only specific AnyConnect and WebVPN configurations. For more information, see the Vulnerable Products section.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Input During Web Page Generation
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
How developers prevent this class of flaw
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples of libraries and frameworks that make it easier to generate properly encoded output include Microsoft's Anti-XSS library, the OWASP ESAPI Encoding module, and Apache Wicket.
- Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.
- For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
More Improper Neutralization of Input During Web Page Generation vulnerabilities (CWE-79)
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-3580US Government Resource
Other vulnerabilities in Cisco Adaptive Security Appliance (ASA) Software
- 9.0 Critical severity
- 8.6 High severity
- 8.6 High severity
- 8.5 High severity
- 7.7 High severity
- 8.6 High severity
Recent Improper Neutralization of Input During Web Page Generation vulnerabilities
- 6.1 Medium severity
- 6.1 Medium severity
JQuery Cross-Site Scripting (XSS) Exploited
- 8.2 High severity
WhatsApp Cross-Site Scripting Exploited
- 6.1 Medium severity
- 6.1 Medium severity
- 6.1 Medium severity
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