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Cisco IOS and IOS XE Software TACACS+ Authentication Bypass Vulnerability

cisco-sa-ios-tacacs-hdB7thJw · High · Published · Updated

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.   Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability. This advisory is available at the following link:https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-tacacs-hdB7thJw This advisory is part of the September 2025 release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2025 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.

Cisco advisory · CSAF JSON

Workarounds

There is a workaround that addresses this vulnerability. Ensure every TACACS+ server that is configured on the device has a shared secret configured.

While this workaround has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.

CVEsCVE-2025-20160
Cisco Bug IDsCSCwm99306
CVSS ScoreBase 8.1
Base 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:X/RL:X/RC:X
Product Names From Source
Cisco IOS 15.2(6)E1, Cisco IOS 15.2(4)E6, Cisco IOS 15.2(6)E2, Cisco IOS 15.2(6)E1a, Cisco IOS 15.2(4)E7, Cisco IOS 15.2(6)E1s, Cisco IOS 15.2(7)E, Cisco IOS 15.2(4)E8, Cisco IOS 15.2(6)E2a, Cisco IOS 15.2(6)E2b, Cisco IOS 15.2(7)E1, Cisco IOS 15.2(7)E0a, Cisco IOS 15.2(7)E0b, Cisco IOS 15.2(7)E0s, Cisco IOS 15.2(6)E3, Cisco IOS 15.2(4)E9, Cisco IOS 15.2(7)E2, Cisco IOS 15.2(7a)E0b, Cisco IOS 15.2(4)E10, Cisco IOS 15.2(7)E3, Cisco IOS 15.2(7)E1a, Cisco IOS 15.2(7b)E0b, Cisco IOS 15.2(7)E2a, Cisco IOS 15.2(4)E10a, Cisco IOS 15.2(7)E4, Cisco IOS 15.2(7)E2b, Cisco IOS 15.2(7)E3k, Cisco IOS 15.2(4)E10b, Cisco IOS 15.2(8)E, Cisco IOS 15.2(8)E1, Cisco IOS 15.2(7)E5, Cisco IOS 15.2(7)E6, Cisco IOS 15.2(8)E2, Cisco IOS 15.2(4)E10c, Cisco IOS 15.2(4)E10d, Cisco IOS 15.2(7)E7, Cisco IOS 15.2(8)E3, Cisco IOS 15.2(7)E8, Cisco IOS 15.2(8)E4, Cisco IOS 15.2(4)E10e, Cisco IOS 15.2(7)E9, Cisco IOS 15.2(8)E5, Cisco IOS 15.2(8)E6, Cisco IOS 15.2(7)E10, Cisco IOS 15.2(7)E11, Cisco IOS 15.2(8)E7, Cisco IOS 15.2(7)E12, Cisco IOS 15.5(3)S8, Cisco IOS 15.5(3)S9, Cisco IOS 15.5(3)S10, Cisco IOS 15.5(3)S9a, Cisco IOS 15.5(3)S10a, Cisco IOS 15.5(3)S10b, Cisco IOS 15.2(6)EB, Cisco IOS 15.5(3)M7, Cisco IOS 15.5(3)M8, Cisco IOS 15.5(3)M9, Cisco IOS 15.5(3)M10, Cisco IOS 15.5(3)M11, Cisco IOS 15.5(3)M11a, Cisco IOS 15.5(3)M11b, Cisco IOS 15.6(2)SP5, Cisco IOS 15.6(2)SP6, Cisco IOS 15.6(2)SP7, Cisco IOS 15.6(2)SP8, Cisco IOS 15.6(2)SP9, Cisco IOS 15.6(2)SP8a, Cisco IOS 15.6(3)M4, Cisco IOS 15.6(3)M5, Cisco IOS 15.6(3)M6, Cisco IOS 15.6(3)M7, Cisco IOS 15.6(3)M6a, Cisco IOS 15.6(3)M6b, Cisco IOS 15.6(3)M8, Cisco IOS 15.6(3)M9, Cisco IOS 15.5(1)SY2, Cisco IOS 15.5(1)SY3, Cisco IOS 15.5(1)SY4, Cisco IOS 15.5(1)SY5, Cisco IOS 15.5(1)SY6, Cisco IOS 15.5(1)SY7, Cisco IOS 15.5(1)SY8, Cisco IOS 15.5(1)SY9, Cisco IOS 15.5(1)SY10, Cisco IOS 15.5(1)SY11, Cisco IOS 15.5(1)SY12, Cisco IOS 15.5(1)SY13, Cisco IOS 15.5(1)SY14, Cisco IOS 15.5(1)SY15, Cisco IOS 15.7(3)M3, Cisco IOS 15.7(3)M2, Cisco IOS 15.7(3)M4, Cisco IOS 15.7(3)M5, Cisco IOS 15.7(3)M4a, Cisco IOS 15.7(3)M4b, Cisco IOS 15.7(3)M6, Cisco IOS 15.7(3)M7, Cisco IOS 15.7(3)M8, Cisco IOS 15.7(3)M9, Cisco IOS 15.7(3)M10, Cisco IOS 15.7(3)M10a, Cisco IOS 15.7(3)M10b, Cisco IOS 15.8(3)M, Cisco IOS 15.8(3)M1, Cisco IOS 15.8(3)M0a, Cisco IOS 15.8(3)M0b, Cisco IOS 15.8(3)M2, Cisco IOS 15.8(3)M1a, Cisco IOS 15.8(3)M3, Cisco IOS 15.8(3)M2a, Cisco IOS 15.8(3)M4, Cisco IOS 15.8(3)M3a, Cisco IOS 15.8(3)M3b, Cisco IOS 15.8(3)M5, Cisco IOS 15.8(3)M6, Cisco IOS 15.8(3)M7, Cisco IOS 15.8(3)M8, Cisco IOS 15.8(3)M9, Cisco IOS 12.2(6)I1, Cisco IOS 15.9(3)M, Cisco IOS 15.9(3)M1, Cisco IOS 15.9(3)M0a, Cisco IOS 15.9(3)M2, Cisco IOS 15.9(3)M3, Cisco IOS 15.9(3)M2a, Cisco IOS 15.9(3)M3a, Cisco IOS 15.9(3)M4, Cisco IOS 15.9(3)M3b, Cisco IOS 15.9(3)M5, Cisco IOS 15.9(3)M4a, Cisco IOS 15.9(3)M6, Cisco IOS 15.9(3)M7, Cisco IOS 15.9(3)M6a, Cisco IOS 15.9(3)M6b, Cisco IOS 15.9(3)M8, Cisco IOS 15.9(3)M7a, Cisco IOS 15.9(3)M8a, Cisco IOS 15.9(3)M9, Cisco IOS 15.9(3)M8b, Cisco IOS 15.9(3)M10, Cisco IOS 15.9(3)M9a, Cisco IOS 15.9(3)M11, Cisco IOS 15.1(3)SVR1, Cisco IOS 15.1(3)SVR2, Cisco IOS 15.1(3)SVR3, Cisco IOS 15.1(3)SVR10, Cisco IOS 15.1(3)SVS, Cisco IOS 15.1(3)SVS1, Cisco IOS 15.1(3)SVT1, Cisco IOS 15.1(3)SVT2, Cisco IOS 15.1(3)SVT3, Cisco IOS 15.1(3)SVT4, Cisco IOS 15.1(3)SVU1, Cisco IOS 15.1(3)SVU10, Cisco IOS 15.1(3)SVU2, Cisco IOS 15.1(3)SVU11, Cisco IOS 15.1(3)SVU20, Cisco IOS 15.1(3)SVU21, Cisco IOS 15.1(3)SVV1, Cisco IOS 15.1(3)SVV2, Cisco IOS 15.1(3)SVV3, Cisco IOS 15.1(3)SVV4, Cisco IOS 15.1(3)SVW, Cisco IOS 15.1(3)SVW1, Cisco IOS 15.1(3)SVX, Cisco IOS 15.1(3)SVX1, Cisco IOS XE Software 3.16.8S, Cisco IOS XE Software 3.16.9S, Cisco IOS XE Software 3.16.10S, Cisco IOS XE Software 3.16.10aS, Cisco IOS XE Software 3.16.10bS, Cisco IOS XE Software 3.8.6E, Cisco IOS XE Software 3.8.7E, Cisco IOS XE Software 3.8.8E, Cisco IOS XE Software 3.8.9E, Cisco IOS XE Software 3.8.10E, Cisco IOS XE Software 3.8.10cE, Cisco IOS XE Software 3.8.10dE, Cisco IOS XE Software 3.18.5SP, Cisco IOS XE Software 3.18.6SP, Cisco IOS XE Software 3.18.7SP, Cisco IOS XE Software 3.18.8aSP, Cisco IOS XE Software 3.18.9SP, Cisco IOS XE Software 16.6.5, Cisco IOS XE Software 16.6.5a, Cisco IOS XE Software 16.6.6, Cisco IOS XE Software 16.6.5b, Cisco IOS XE Software 16.6.7, Cisco IOS XE Software 16.6.7a, Cisco IOS XE Software 16.6.8, Cisco IOS XE Software 16.6.9, Cisco IOS XE Software 16.6.10, Cisco IOS XE Software 16.8.1, Cisco IOS XE Software 16.8.1a, Cisco IOS XE Software 16.8.1b, Cisco IOS XE Software 16.8.1s, Cisco IOS XE Software 16.8.1c, Cisco IOS XE Software 16.8.1d, Cisco IOS XE Software 16.8.2, Cisco IOS XE Software 16.8.1e, Cisco IOS XE Software 16.8.3, Cisco IOS XE Software 16.9.1, Cisco IOS XE Software 16.9.2, Cisco IOS XE Software 16.9.1a, Cisco IOS XE Software 16.9.1b, Cisco IOS XE Software 16.9.1s, Cisco IOS XE Software 16.9.1c, Cisco IOS XE Software 16.9.1d, Cisco IOS XE Software 16.9.3, Cisco IOS XE Software 16.9.2a, Cisco IOS XE Software 16.9.2s, Cisco IOS XE Software 16.9.3h, Cisco IOS XE Software 16.9.4, Cisco IOS XE Software 16.9.3s, Cisco IOS XE Software 16.9.3a, Cisco IOS XE Software 16.9.4c, Cisco IOS XE Software 16.9.5, Cisco IOS XE Software 16.9.5f, Cisco IOS XE Software 16.9.6, Cisco IOS XE Software 16.9.7, Cisco IOS XE Software 16.9.8, Cisco IOS XE Software 16.9.8a, Cisco IOS XE Software 16.9.8b, Cisco IOS XE Software 16.10.1, Cisco IOS XE Software 16.10.1a, Cisco IOS XE Software 16.10.1b, Cisco IOS XE Software 16.10.1s, Cisco IOS XE Software 16.10.1c, Cisco IOS XE Software 16.10.1e, Cisco IOS XE Software 16.10.1d, Cisco IOS XE Software 16.10.2, Cisco IOS XE Software 16.10.1f, Cisco IOS XE Software 16.10.1g, Cisco IOS XE Software 16.10.3, Cisco IOS XE Software 3.10.1E, Cisco IOS XE Software 3.10.2E, Cisco IOS XE Software 3.10.1aE, Cisco IOS XE Software 3.10.1sE, Cisco IOS XE Software 3.10.3E, Cisco IOS XE Software 16.11.1, Cisco IOS XE Software 16.11.1a, Cisco IOS XE Software 16.11.1b, Cisco IOS XE Software 16.11.2, Cisco IOS XE Software 16.11.1s, Cisco IOS XE Software 16.11.1c, Cisco IOS XE Software 16.12.1, Cisco IOS XE Software 16.12.1s, Cisco IOS XE Software 16.12.1a, Cisco IOS XE Software 16.12.1c, Cisco IOS XE Software 16.12.1w, Cisco IOS XE Software 16.12.2, Cisco IOS XE Software 16.12.1y, Cisco IOS XE Software 16.12.2a, Cisco IOS XE Software 16.12.3, Cisco IOS XE Software 16.12.8, Cisco IOS XE Software 16.12.2s, Cisco IOS XE Software 16.12.1x, Cisco IOS XE Software 16.12.1t, Cisco IOS XE Software 16.12.2t, Cisco IOS XE Software 16.12.4, Cisco IOS XE Software 16.12.3s, Cisco IOS XE Software 16.12.1z, Cisco IOS XE Software 16.12.3a, Cisco IOS XE Software 16.12.4a, Cisco IOS XE Software 16.12.5, Cisco IOS XE Software 16.12.6, Cisco IOS XE Software 16.12.1z1, Cisco IOS XE Software 16.12.5a, Cisco IOS XE Software 16.12.5b, Cisco IOS XE Software 16.12.1z2, Cisco IOS XE Software 16.12.6a, Cisco IOS XE Software 16.12.7, Cisco IOS XE Software 16.12.9, Cisco IOS XE Software 16.12.10, Cisco IOS XE Software 16.12.10a, Cisco IOS XE Software 16.12.11, Cisco IOS XE Software 16.12.12, Cisco IOS XE Software 16.12.13, Cisco IOS XE Software 3.11.0E, Cisco IOS XE Software 3.11.1E, Cisco IOS XE Software 3.11.2E, Cisco IOS XE Software 3.11.3E, Cisco IOS XE Software 3.11.1aE, Cisco IOS XE Software 3.11.2aE, Cisco IOS XE Software 3.11.4E, Cisco IOS XE Software 3.11.3aE, Cisco IOS XE Software 3.11.5E, Cisco IOS XE Software 3.11.6E, Cisco IOS XE Software 3.11.7E, Cisco IOS XE Software 3.11.8E, Cisco IOS XE Software 3.11.9E, Cisco IOS XE Software 3.11.10E, Cisco IOS XE Software 3.11.11E, Cisco IOS XE Software 3.11.12E, Cisco IOS XE Software 17.1.1, Cisco IOS XE Software 17.1.1a, Cisco IOS XE Software 17.1.1s, Cisco IOS XE Software 17.1.2, Cisco IOS XE Software 17.1.1t, Cisco IOS XE Software 17.1.3, Cisco IOS XE Software 17.2.1, Cisco IOS XE Software 17.2.1r, Cisco IOS XE Software 17.2.1a, Cisco IOS XE Software 17.2.1v, Cisco IOS XE Software 17.2.2, Cisco IOS XE Software 17.2.3, Cisco IOS XE Software 17.3.1, Cisco IOS XE Software 17.3.2, Cisco IOS XE Software 17.3.3, Cisco IOS XE Software 17.3.1a, Cisco IOS XE Software 17.3.1w, Cisco IOS XE Software 17.3.2a, Cisco IOS XE Software 17.3.1x, Cisco IOS XE Software 17.3.1z, Cisco IOS XE Software 17.3.3a, Cisco IOS XE Software 17.3.4, Cisco IOS XE Software 17.3.5, Cisco IOS XE Software 17.3.4a, Cisco IOS XE Software 17.3.6, Cisco IOS XE Software 17.3.4b, Cisco IOS XE Software 17.3.4c, Cisco IOS XE Software 17.3.5a, Cisco IOS XE Software 17.3.5b, Cisco IOS XE Software 17.3.7, Cisco IOS XE Software 17.3.8, Cisco IOS XE Software 17.3.8a, Cisco IOS XE Software 17.4.1, Cisco IOS XE Software 17.4.2, Cisco IOS XE Software 17.4.1a, Cisco IOS XE Software 17.4.1b, Cisco IOS XE Software 17.4.1c, Cisco IOS XE Software 17.4.2a, Cisco IOS XE Software 17.5.1, Cisco IOS XE Software 17.5.1a, Cisco IOS XE Software 17.6.1, Cisco IOS XE Software 17.6.2, Cisco IOS XE Software 17.6.1w, Cisco IOS XE Software 17.6.1a, Cisco IOS XE Software 17.6.1x, Cisco IOS XE Software 17.6.3, Cisco IOS XE Software 17.6.1y, Cisco IOS XE Software 17.6.1z, Cisco IOS XE Software 17.6.3a, Cisco IOS XE Software 17.6.4, Cisco IOS XE Software 17.6.1z1, Cisco IOS XE Software 17.6.5, Cisco IOS XE Software 17.6.6, Cisco IOS XE Software 17.6.6a, Cisco IOS XE Software 17.6.5a, Cisco IOS XE Software 17.6.7, Cisco IOS XE Software 17.6.8, Cisco IOS XE Software 17.6.8a, Cisco IOS XE Software 17.7.1, Cisco IOS XE Software 17.7.1a, Cisco IOS XE Software 17.7.1b, Cisco IOS XE Software 17.7.2, Cisco IOS XE Software 17.10.1, Cisco IOS XE Software 17.10.1a, Cisco IOS XE Software 17.10.1b, Cisco IOS XE Software 17.8.1, Cisco IOS XE Software 17.8.1a, Cisco IOS XE Software 17.9.1, Cisco IOS XE Software 17.9.1w, Cisco IOS XE Software 17.9.2, Cisco IOS XE Software 17.9.1a, Cisco IOS XE Software 17.9.1x, Cisco IOS XE Software 17.9.1y, Cisco IOS XE Software 17.9.3, Cisco IOS XE Software 17.9.2a, Cisco IOS XE Software 17.9.1x1, Cisco IOS XE Software 17.9.3a, Cisco IOS XE Software 17.9.4, Cisco IOS XE Software 17.9.1y1, Cisco IOS XE Software 17.9.5, Cisco IOS XE Software 17.9.4a, Cisco IOS XE Software 17.9.5a, Cisco IOS XE Software 17.9.5b, Cisco IOS XE Software 17.9.6, Cisco IOS XE Software 17.9.5c, Cisco IOS XE Software 17.9.5d, Cisco IOS XE Software 17.9.6a, Cisco IOS XE Software 17.9.6b, Cisco IOS XE Software 17.9.7, Cisco IOS XE Software 17.9.5e, Cisco IOS XE Software 17.9.5f, Cisco IOS XE Software 17.9.7a, Cisco IOS XE Software 17.9.7b, Cisco IOS XE Software 17.11.1, Cisco IOS XE Software 17.11.1a, Cisco IOS XE Software 17.12.1, Cisco IOS XE Software 17.12.1w, Cisco IOS XE Software 17.12.1a, Cisco IOS XE Software 17.12.1x, Cisco IOS XE Software 17.12.2, Cisco IOS XE Software 17.12.3, Cisco IOS XE Software 17.12.2a, Cisco IOS XE Software 17.12.1y, Cisco IOS XE Software 17.12.1z, Cisco IOS XE Software 17.12.4, Cisco IOS XE Software 17.12.3a, Cisco IOS XE Software 17.12.1z1, Cisco IOS XE Software 17.12.1z2, Cisco IOS XE Software 17.12.4a, Cisco IOS XE Software 17.12.5, Cisco IOS XE Software 17.12.4b, Cisco IOS XE Software 17.12.1z3, Cisco IOS XE Software 17.12.5a, Cisco IOS XE Software 17.12.1z4, Cisco IOS XE Software 17.12.5b, Cisco IOS XE Software 17.12.5c, Cisco IOS XE Software 17.13.1, Cisco IOS XE Software 17.13.1a, Cisco IOS XE Software 17.14.1, Cisco IOS XE Software 17.14.1a, Cisco IOS XE Software 17.11.99SW, Cisco IOS XE Software 17.15.1, Cisco IOS XE Software 17.15.1w, Cisco IOS XE Software 17.15.1a, Cisco IOS XE Software 17.15.2, Cisco IOS XE Software 17.15.1b, Cisco IOS XE Software 17.15.1x, Cisco IOS XE Software 17.15.3, Cisco IOS XE Software 17.15.2c, Cisco IOS XE Software 17.15.2a, Cisco IOS XE Software 17.15.1y, Cisco IOS XE Software 17.15.2b, Cisco IOS XE Software 17.15.3a, Cisco IOS XE Software 17.15.3b, Cisco IOS, Cisco IOS XE Software

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