# CVE-2023-26258: Arcserve UDP - Authentication Bypass

> Live exploitation tracking for CVE-2023-26258 by the CrowdSec Live Exploit Tracker, built from real-world attack data crowdsourced from CrowdSec's global network.

Page: https://tracker.crowdsec.net/cves/CVE-2023-26258

## Key facts

- **Exploitation phase:** Limited Exploitation. The vulnerability is known but shows very limited attacker interest or exploitation activity.
- **CVSS score:** 9.8
- **Public exploit available:** Yes
- **Affected products:** Arcserve UDP
- **Weaknesses:** CWE-863 (Incorrect Authorization)
- **Tags:** enterprise_software

## Description

Arcserve UDP through 9.0.6034 allows authentication bypass. The method getVersionInfo at WebServiceImpl/services/FlashServiceImpl leaks the AuthUUID token. This token can be used at /WebServiceImpl/services/VirtualStandbyServiceImpl to obtain a valid session. This session can be used to execute any task as administrator.

## CrowdSec analysis

[CVE-2023-26258](https://euvd.enisa.europa.eu/vulnerability/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.

## Timeline

- 2023-07-03: CVE Published. CVE-2023-26258 is published to NVD.
- 2025-10-15: Rule Released. CrowdSec releases a rule to detect CVE-2023-26258 exploitation attempts against the CrowdSec Network.
- 2025-10-16: CrowdSec First Seen. CrowdSec observes in-the-wild exploitation of CVE-2023-26258 for the first time.

## References

- https://www.mdsec.co.uk/2023/06/cve-2023-26258-remote-code-execution-in-arcserve-udp-backup/
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2023/CVE-2023-26258.yaml

## Live exploitation data

The [Live Exploit Tracker page](https://tracker.crowdsec.net/cves/CVE-2023-26258) follows observed exploitation activity for CVE-2023-26258. [Request an API key](https://tracker.crowdsec.net/request-api-key) for full access to its exploitation timeline, attacking IP addresses and blocklists.