A vulnerability in the MIT Kerberos implementation allows GSSAPI-protected messages using RC4-HMAC-MD5 to be spoofed due to weaknesses in the MD5 checksum design. If RC4 is preferred over stronger encryption types, an attacker could exploit MD5 collisions to forge message integrity codes. This may lead to unauthorized message tampering.

redhat RHSA-2025:9430: RHSA-2025:9430: krb5 security update (Moderate)

oracle_linux ELSA-2025-9430: ELSA-2025-9430:  krb5 security update (MODERATE)

redhat RHSA-2025:9418: RHSA-2025:9418: krb5 security update (Moderate)

The remote Fedora 41 host has a package installed that is affected by a vulnerability as referenced in the FEDORA-2025-42a13f896e advisory.

    * Disallowing use of the `arcfour-hmac(-md5)` encryption type for session keys
    * Add support for the PKINIT paChecksum2 sequence, required for Active Directory interoperability on     Windows Server 2025
    * Fix generation of RADIUS Message-Authenticator in FIPS mode


Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Fedora 42 host has a package installed that is affected by a vulnerability as referenced in the FEDORA-2025-3de9fe91ff advisory.

    * Disallowing use of the `arcfour-hmac(-md5)` encryption type for session keys
    * Add support for the PKINIT paChecksum2 sequence, required for Active Directory interoperability on     Windows Server 2025
    * Fix generation of RADIUS Message-Authenticator in FIPS mode



Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Fedora 43 host has a package installed that is affected by a vulnerability as referenced in the FEDORA-2025-1c915db8a5 advisory.

    Automatic update for krb5-1.21.3-6.fc43.

    ##### **Changelog**

    ```
    * Wed Jun  4 2025 Julien Rische <jrische@redhat.com> - 1.21.3-6
    - Do not block HMAC-MD4/5 in FIPS mode       Resolves: rhbz#2370259
    - PKINIT: implement paChecksum2 from MS-PKCA v20230920       Resolves: rhbz#2357215
    - Disallow RC4 HMAC-MD5 session keys by default (CVE-2025-3576)       Resolves: rhbz#2359705

    ```

Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote AlmaLinux 8 host has packages installed that are affected by a vulnerability as referenced in the ALSA-2025:8411 advisory.

    * krb5: Kerberos RC4-HMAC-MD5 Checksum Vulnerability Enabling Message Spoofing via MD5 Collisions     (CVE-2025-3576)

Tenable has extracted the preceding description block directly from the AlmaLinux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Oracle Linux 8 host has packages installed that are affected by a vulnerability as referenced in the ELSA-2025-8411 advisory.

    - Don't issue RC4 session keys by default (CVE-2025-3576)       Resolves: RHEL-88049

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Redhat Enterprise Linux 8 host has packages installed that are affected by a vulnerability as referenced in the RHSA-2025:8411 advisory.

    Kerberos is a network authentication system, which can improve the security of your network by eliminating     the insecure practice of sending passwords over the network in unencrypted form. It allows clients and     servers to authenticate to each other with the help of a trusted third party, the Kerberos key     distribution center (KDC).

    Security Fix(es):

    * krb5: Kerberos RC4-HMAC-MD5 Checksum Vulnerability Enabling Message Spoofing via MD5 Collisions     (CVE-2025-3576)

    For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and     other related information, refer to the CVE page(s) listed in the References section.

Tenable has extracted the preceding description block directly from the Red Hat Enterprise Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Debian 11 host has packages installed that are affected by a vulnerability as referenced in the dla-4195 advisory.

    - -------------------------------------------------------------------------     Debian LTS Advisory DLA-4195-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                   Bastien Roucaris     May 30, 2025                                  https://wiki.debian.org/LTS
    - -------------------------------------------------------------------------

    Package        : krb5     Version        : 1.18.3-6+deb11u7     CVE ID         : CVE-2025-3576     Debian Bug     : 1103525

    A Vulnerability in the MIT Kerberos implementation     allows GSSAPI-protected messages using RC4-HMAC-MD5     to be spoofed due to weaknesses in the MD5 checksum design.
    If RC4 is preferred over stronger encryption types,     an attacker could exploit MD5 collisions to forge message     integrity codes. This may lead to unauthorized     message tampering.

    In order to fix CVE-2025-3576, vulnerable cryptographic     algorithms for tickets need to be disabled explicitly     with the new allow_rc4 or allow_des3 variables.

    According to the vulnerability report Kerberos?? RC4-HMAC broken     in practice: spoofing PACs with MD5 collisions, disabling     this cryptographic algorithm may break some older     authentication systems, and administrators should test carefully.

    Because of the risk of breaking certain configurations, the     new allow_rc4 or allow_des3 are being treated as having a     default value of 'true' for updates to older Debian releases.
    This leaves the 3DES and RC4 algorithms enabled, but administrators     are strongly encouraged to disable them after verifying     compatibility in their environments.

    For Debian 11 bullseye, this problem has been fixed in version     1.18.3-6+deb11u7.

    We recommend that you upgrade your krb5 packages.

    For the detailed security status of krb5 please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/krb5

    Further information about Debian LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS host has packages installed that are affected by a vulnerability as referenced in the USN-7542-1 advisory.

    It was discovered that Kerberos allowed the usage of weak cryptographic standards. An attacker could     possibly use this issue to expose sensitive information.

    This update introduces the allow_rc4 and allow_des3 configuration options, and disables the usage of RC4     and 3DES ciphers by default. Users are advised to discontinue their usage and upgrade to stronger     encryption protocols. If the use of the insecure RC4 and 3DES algorithms is necessary, they can be enabled     with the aforementioned configuration options.

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
238038	Fedora 41 : krb5 (2025-42a13f896e)	Nessus	Fedora Local Security Checks	medium
237971	Fedora 42 : krb5 (2025-3de9fe91ff)	Nessus	Fedora Local Security Checks	medium
237911	Fedora 43 : krb5 (2025-1c915db8a5)	Nessus	Fedora Local Security Checks	medium
237724	AlmaLinux 8 : krb5 (ALSA-2025:8411)	Nessus	Alma Linux Local Security Checks	medium
237720	Oracle Linux 8 : krb5 (ELSA-2025-8411)	Nessus	Oracle Linux Local Security Checks	medium
237689	RHEL 8 : krb5 (RHSA-2025:8411)	Nessus	Red Hat Local Security Checks	medium
237586	Debian dla-4195 : krb5-admin-server - security update	Nessus	Debian Local Security Checks	medium
237448	Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS : Kerberos vulnerability (USN-7542-1)	Nessus	Ubuntu Local Security Checks	medium

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