Arcserve UDP - Authentication Bypass (CVE-2023-26258)

CVE-2023-26258 is a critical authentication bypass vulnerability in Arcserve UDP through version 9.0.6034, where the getVersionInfo method leaks an AuthUUID token. Attackers can exploit this flaw to obtain a valid administrator session and execute any task with full privileges, potentially leading to complete system compromise.

CrowdSec has been tracking this vulnerability and its exploits since 15th of October 2025.

CrowdSec network observations suggest that most exploitation of CVE-2023-26258 involves focused reconnaissance to identify viable targets. Attackers typically tailor their campaigns based on system exposure and configuration. It is unlikely that a given attack is accidental. Data from the CrowdSec community also indicates a gradual decrease in attacks targeting CVE-2023-26258. While still present in the wild, exploitation levels have dropped noticeably week-over-week. This may signal that the vulnerability is becoming less relevant or that defenses are improving fast enough for attackers to lose interest.

Attackers exploit Arcserve UDP servers by sending crafted SOAP requests to endpoints such as /WebServiceImpl/services/FlashServiceImpl and /WebServiceImpl/services/VirtualStandbyServiceImpl to bypass authentication and obtain administrative session tokens. These endpoints are targeted to leak sensitive tokens and escalate privileges without valid credentials.