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CVE-2025-20160VulnerabilityPublished Updated

CVE-2025-20160: Cisco IOS · Improper Authentication

Affects Cisco IOSSource CVE Database V5

0

Not known to be exploited · CVSS 8.1 High.

Data as of 26 Oct 2026, 06:15 UTC

CVSS 3.1 base score
8.1High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 37% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Sep 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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 2026-10-25.

What to do

AI-suggested

1. Immediately audit all Cisco IOS and IOS XE devices to identify affected versions and TACACS+ configurations. 2. Apply Cisco's security patches or updates as soon as they become available for the affected software versions. 3. Ensure that TACACS+ shared secrets are properly configured and enforced on all devices to prevent acceptance of unauthenticated requests. 4. Deploy TACACS+ over secure transport mechanisms such as IPsec or VPN tunnels to protect against man-in-the-middle interception of unencrypted messages. 5. Consider migrating to more secure authentication protocols like RADIUS with encryption or TACACS+ implementations that support encryption of payloads. 6. Monitor network traffic for unusual TACACS+ activity or authentication anomalies that could indicate exploitation attempts. 7. Restrict network access to TACACS+ servers and devices using access control lists (ACLs) and segmentation to limit exposure. 8. Conduct regular security assessments and penetration testing to verify the effectiveness of mitigations. 9. Educate network administrators on this vulnerability and the importance of secure TACACS+ configurations. 10. Implement multi-factor authentication (MFA) where possible to add an additional layer of security beyond TACACS+.

Description

A vulnerability in the implementation of the TACACS+ protocol in Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to view sensitive data or bypass authentication. This vulnerability exists because the system does not properly check whether the required TACACS+ shared secret is configured. A machine-in-the-middle attacker could exploit this vulnerability by intercepting and reading unencrypted TACACS+ messages or impersonating the TACACS+ server and falsely accepting arbitrary authentication requests. A successful exploit could allow the attacker to view sensitive information in a TACACS+ message or bypass authentication and gain access to the affected device.

References

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