CVE-2025-20343VulnerabilityPublished 5 Nov 2025

CVE-2025-20343: Cisco Identity Services Engine Software · Incorrect Comparison

Affects Cisco Identity Services Engine SoftwareSource CVE Database V5

Not known to be exploited · CVSS 8.6 High.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

8.6High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.7% chance of exploitation in 30 days – higher than 53% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 5 Nov 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Cisco Cisco Identity Services Engine Software	Affected =3.4.0	Fixed in–

AI-suggested

1. Apply Cisco's official patches or updates for Cisco ISE versions 3.4.0 through 3.4 Patch 3 as soon as they become available to address the logic error in RADIUS request processing. 2. Monitor RADIUS traffic for unusual patterns, such as repeated access requests from the same MAC addresses that are already rejected, which could indicate exploitation attempts. 3. Implement network segmentation to isolate Cisco ISE servers from untrusted or less secure network segments, reducing exposure to remote attacks. 4. Employ rate limiting or filtering on RADIUS requests to mitigate the impact of repeated crafted requests targeting rejected endpoints. 5. Maintain robust logging and alerting on Cisco ISE to detect unexpected restarts or service disruptions promptly. 6. Conduct regular security assessments and penetration testing focusing on network access control infrastructure to identify potential weaknesses. 7. Educate network administrators about this vulnerability and ensure incident response plans include steps for handling Cisco ISE service disruptions.

Description

A vulnerability in the RADIUS setting Reject RADIUS requests from clients with repeated failures on Cisco Identity Services Engine (ISE) could allow an unauthenticated, remote attacker to cause Cisco ISE to restart unexpectedly. This vulnerability is due to a logic error when processing a RADIUS access request for a MAC address that is already a rejected endpoint. An attacker could exploit this vulnerability by sending a specific sequence of multiple crafted RADIUS access request messages to Cisco ISE. A successful exploit could allow the attacker to cause a denial of service (DoS) condition when Cisco ISE restarts.

Impact

For European organizations, the impact of CVE-2025-20343 is primarily a denial of service against Cisco ISE, which is critical for network access control and authentication. A successful exploit can cause Cisco ISE to restart repeatedly, disrupting authentication services and potentially allowing unauthorized network access or causing legitimate users to lose connectivity. This can affect enterprise networks, government agencies, and critical infrastructure sectors that depend on Cisco ISE for enforcing security policies. The resulting downtime can lead to operational disruptions, increased risk of security breaches due to lapses in access control, and potential regulatory compliance issues under frameworks like GDPR if network security is compromised. The lack of confidentiality or integrity impact limits data breach risks, but availability loss in security infrastructure is a significant concern. Organizations with large-scale deployments of Cisco ISE or those in sectors requiring high availability and strict access control are at elevated risk.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ise-radsupress-dos-8YF3JThh (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Nov 2025, 17:13 UTC

Technical details

References

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