Cisco Secure Firewall Adaptive Security…: Use of Insufficiently Random Values
CVE-2026-20101 is a high-severity use of insufficiently random values vulnerability in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software from Cisco, with a CVSS 3.1 base score of 8.6 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Cisco Secure Firewall Adaptive Security Appliance (ASA) Software versions: 9.12.1; 9.12.1.2; 9.12.1.3, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.4% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Adaptive Security Appliance Software to 9.16.4.85 or 9.18.4.66 or 9.20.4 or 9.22.2.4, whichever matches your release line, or a later version.
- Update Secure Firewall Threat Defense to 7.0.9 or 7.2.11 or 7.4.3 or 7.6.4, whichever matches your release line, or a later version.
- Read the advisory on sec.cloudapps.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.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Cisco | Cisco Secure Firewall Adaptive Security Appliance (ASA) Software | 9.12.1; 9.12.1.2; 9.12.1.3; 9.12.2; 9.12.2.4; 9.12.2.5; 9.12.2.9; 9.12.3; and 32 more ranges | Not stated |
| Cisco | Cisco Secure Firewall Threat Defense (FTD) Software | 6.4.0; 6.4.0.1; 6.4.0.3; 6.4.0.2; 6.4.0.4; 6.4.0.5; 6.4.0.6; 6.4.0.7; and 32 more ranges | Not stated |
| Cisco | Adaptive Security Appliance Software | 9.12.1 up to, but not including, 9.16.4.85; 9.17.1 up to, but not including, 9.18.4.66; 9.19.1 up to, but not including, 9.20.4; 9.22.1.1 up to, but not including, 9.22.2.4; 9.23.1 up to, but not including, 9.23.1.7 | 9.16.4.85, 9.18.4.66, 9.20.4, 9.22.2.4, 9.23.1.7 |
| Cisco | Secure Firewall Threat Defense | 6.4.0 up to, but not including, 7.0.9; 7.1.0 up to, but not including, 7.2.11; 7.3.0 up to, but not including, 7.4.3; 7.6.0 up to, but not including, 7.6.4; 7.7.0 up to, but not including, 7.7.11 | 7.0.9, 7.2.11, 7.4.3, 7.6.4, 7.7.11 |
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
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H. Scored by CNA (cisco.com).
Official description
A vulnerability in the SAML 2.0 single sign-on (SSO) feature of Cisco Secure Firewall ASA Software and Secure FTD Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a DoS condition. This vulnerability is due to insufficient error checking when processing SAML messages. An attacker could exploit this vulnerability by sending crafted SAML messages to the SAML service. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use of Insufficiently Random Values
The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.
How developers prevent this class of flaw
- Use a well-vetted algorithm that is currently considered to be strong by experts in the field, and select well-tested implementations with adequate length seeds. In general, if a pseudo-random number generator is not advertised as being cryptographically secure, then it is probably a statistical PRNG and should not be used in security-sensitive contexts. Pseudo-random number generators can produce predictable numbers if the generator is known and the seed can be guessed. A 256-bit seed is a good starting point for producing a random enough number.
- Consider a PRNG that re-seeds itself as needed from high quality pseudo-random output sources, such as hardware devices.
- Use products or modules that conform to FIPS 140-2 to avoid obvious entropy problems. Consult FIPS 140-2 Annex C (Approved Random Number Generators).
More Use of Insufficiently Random Values vulnerabilities (CWE-330)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
- 8.6 High severity
- 8.8 High severity
- 8.1 High severity
- 8.4 High severity
- 8.8 High severity
- 9.9 Critical severity
Recent Use of Insufficiently Random Values vulnerabilities
- 9.8 Critical severity
- 9.8 Critical severity
- 7.5 High severity
- 9.1 Critical severity
- 9.8 Critical severity
- 7.5 High severity
Spotted an error? Tell us.