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Serious Vulnerability Exposes Admin Interface of Arcserve UDP Backup Solution

Researchers publish PoC for a high-severity authentication bypass vulnerability in the Arcserve UDP data backup solution.

Proof-of-concept (PoC) code targeting a high-severity authentication bypass vulnerability in the Arcserve Unified Data Protection (UDP) backup software was published one day after patches were released earlier this week.

Tracked as CVE-2023-26258, the security defect was identified in the web management interface of Arcserve UDP. Successful exploitation of the bug could allow an attacker to access the administrative interface.

According to MDSec, the flaw was discovered in the way HTTP requests containing login information were transmitted between the web browser and the administrative interface.

Specifically, MDSec’s security researchers observed that a user validation method being invoked creates a client acting as a proxy that communicates with a web service responsible for validating the supplied credentials.

Because the location of the web service is supplied in the request, the researchers were able to modify the request so that the client would contact an HTTP server controlled by them.

Further analysis of the requests transmitted between the client and the web service allowed the researchers to identify information such as OS version, domain name, and administrator account name, along with a method that validates users by UUID, and an AuthUUID value.

Once they supplied the AuthUUID value to the web service, the researchers received the cookie for a valid administrator session in response, which allowed them to retrieve the encrypted password for that account.

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MDSec reported the vulnerability in early February 2023. A patch was released on June 27, roughly four months after a CVE identifier was assigned to the bug.

Arcserve UDP 9.1 resolves CVE-2023-26258, along with an Apache Commons FileUpload (CVE-2023-24998) flaw, three Spring Framework vulnerabilities made public last year, and various other issues.

On June 28, MDSec released PoC code exploiting the vulnerability to retrieve encrypted passwords, along with additional tools to decrypt the credentials.

MDSec claims that, even if the Arcserve UDP instances are patched against this vulnerability, an attacker on the local network could scan for Arcserve instances that are using default credentials, or may attempt to retrieve the credentials from the Windows registry or using the Remote Registry service.

Related: Fortinet Patches Critical RCE Vulnerability in FortiNAC

Related: CISA Says Critical Zyxel NAS Vulnerability Exploited in Attacks

Related: PoC Exploit Published for Cisco AnyConnect Secure Vulnerability

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

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