#VU55287 NULL pointer dereference in Kerberos 5 - CVE-2021-36222

Vulnerability identifier: #VU55287

Vulnerability risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-36222

CWE-ID: CWE-476

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Kerberos 5
Client/Desktop applications / Software for system administration

Vendor: MIT

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to a NULL pointer dereference error in kdc/kdc_preauth_ec.c in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5). A remote attacker can send a request containing a PA-ENCRYPTED-CHALLENGE padata element without using FAST and perform a denial of service (DoS) attack.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Kerberos 5: 1.2 - 1.19.1

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External links
https://github.com/krb5/krb5/releases
https://web.mit.edu/kerberos/advisories/
https://github.com/krb5/krb5/commit/fc98f520caefff2e5ee9a0026fdf5109944b3562

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.