Cisco Identity Services Engine Software: Authentication Bypass by Spoofing
CVE-2026-76423 is a critical-severity authentication bypass by spoofing vulnerability in Cisco Identity Services Engine Software from Cisco, with a CVSS 3.1 base score of 10.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Cisco Identity Services Engine Software versions: 3.1.0; 3.1.0 p1; 3.1.0 p3, 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 0.58% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of Cisco Identity Services Engine Software you run against the affected versions below, and install the vendor's latest release.
- 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 Identity Services Engine Software | 3.1.0; 3.1.0 p1; 3.1.0 p3; 3.1.0 p2; 3.2.0; 3.1.0 p4; 3.1.0 p5; 3.2.0 p1; and 32 more ranges | Not stated |
| Cisco | Cisco ISE Passive Identity Connector | 3.2.0; 3.1.0; 3.3.0; 3.4.0; 3.5.0 | Not stated |
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
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- LowPerformance or availability is reduced.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L. Scored by CNA (cisco.com).
Official description
A vulnerability in the REST API of Cisco ISE and Cisco ISE-PIC could allow an unauthenticated, remote attacker to gain administrative access to an affected device. This vulnerability is due to the REST API web service being exposed with insufficient authorization checks. An attacker could exploit this vulnerability by sending a crafted HTTP request to the exposed REST API port. A successful exploit could allow the attacker to read and modify ISE configuration and identity data with administrative privileges.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Authentication Bypass by Spoofing
This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.
More Authentication Bypass by Spoofing vulnerabilities (CWE-290)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in Cisco Identity Services Engine Software
- 10.0 Critical severity
- 7.6 High severity
- 7.2 High severity
- 8.6 High severity
- 7.1 High severity
- 9.1 Critical severity
Recent Authentication Bypass by Spoofing vulnerabilities
- 9.1 Critical severity
- 8.7 High severity
- 7.4 High severity
- 9.1 Critical severity
- 9.5 Critical severity
- 9.1 Critical severity
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