# CVE-2025-34521: Arcserve UDP < 10.2 Reflected Cross-Site Scripting (XSS)

> Remote attackers can execute arbitrary JavaScript in victims' browsers via crafted links, potentially leading to session hijacking or credential theft.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 27 Aug 2025
- **Updated:** 15 May 2026
- **Also known as:** GHSA-h6g8-8gr5-822r

## What is CVE-2025-34521?

CVE-2025-34521 is a medium-severity cross-site scripting vulnerability in Arcserve Unified Data Protection (UDP), published on 27 Aug 2025. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

A reflected cross-site scripting (XSS) vulnerability exists in the web interface of the Arcserve Unified Data Protection (UDP), where unsanitized user input is improperly reflected in HTTP responses. This flaw allows remote attackers with low privileges to craft malicious links that, when visited by another user, execute arbitrary JavaScript in the victim’s browser. Successful exploitation may lead to session hijacking, credential theft, or other client-side impacts. The vulnerability requires user interaction and occurs within a shared browser context. This vulnerability affects all UDP versions prior to 10.2. UDP 10.2 includes the necessary patches and requires no action. Versions 8.0 through 10.1 are supported and require either patch application or upgrade to 10.2. Versions 7.x and earlier are unsupported or out of maintenance and must be upgraded to 10.2 to remediate the issue.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2025-34521?

It affects 1 product.


Products: Arcserve Udp.

## How do I fix CVE-2025-34521?

No fix has been published for CVE-2025-34521 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-34521 being exploited?

There is no known exploitation of CVE-2025-34521 in the wild and no public exploit code.

## Other vulnerabilities in Arcserve Unified Data Protection (UDP)

- [CVE-2015-4068](https://insights.sbomify.com/CVE-2015-4068/): Arcserve Unified Data Protection (UDP) Directory Traversal (critical 9.1, exploited in the wild)
- [CVE-2024-0799](https://insights.sbomify.com/CVE-2024-0799/): Authentication Bypass via wizardLogin in Arcserve Unified Data Protection (critical 9.8)
- [CVE-2023-41998](https://insights.sbomify.com/CVE-2023-41998/): Arcserve UDP Unauthenticated RCE (critical 9.8)
- [CVE-2023-41999](https://insights.sbomify.com/CVE-2023-41999/): Arcserve UDP Management Authentication Bypass (critical 9.8)
- [CVE-2023-42000](https://insights.sbomify.com/CVE-2023-42000/): Arcserve UDP Agent Unauthenticated Path Traversal File Upload (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-34521 and fix it if it is affected.

What it is: CVE-2025-34521 is a medium-severity cross-site scripting vulnerability in Arcserve Unified Data Protection (UDP), published on 27 Aug 2025. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2025-34521 in the wild and no public exploit code.

Affected product: Arcserve Unified Data Protection (UDP). No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-34521/ (Markdown: https://insights.sbomify.com/CVE-2025-34521/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-34521
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-34521
- OSV: https://osv.dev/vulnerability/CVE-2025-34521

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From sbomify Insights: https://insights.sbomify.com/CVE-2025-34521/
Summaries are generated and may contain mistakes; the official description above is the record.