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

Status: published. Published: 2026-11-03. Updated: 2026-11-09.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/amir1376/ab-download-manager/commit/34cd27af6a9a6c2046af112bc9bd34828fec0bbc

## Affected products and versions

- amir1376 / ab-download-manager: ≥ 0; < 1.11.2 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 8.7 (high); 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; source: CNA: VulnCheck

- CVSS 3.1: 8.8 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H; source: CNA: VulnCheck

- CVSS 4.0: 8.7 (high); 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 8.8 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.29% as of 2026-11-09; percentile 21.75%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-352

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/amir1376/ab-download-manager/issues/1489 (CNA: VulnCheck; issue-tracking)

- https://github.com/amir1376/ab-download-manager (CNA: VulnCheck; product)

- https://github.com/amir1376/ab-download-manager/commit/34cd27af6a9a6c2046af112bc9bd34828fec0bbc (CNA: VulnCheck; patch)

- https://github.com/amir1376/ab-download-manager/blob/v1.11.1/integration/server/src/main/kotlin/com/abdownloadmanager/integration/Endpoints.kt#L27-L75 (CNA: VulnCheck; technical-description)

- https://github.com/amir1376/ab-download-manager/blob/v1.11.1/desktop/app/src/main/kotlin/com/abdownloadmanager/desktop/integration/IntegrationHandlerImp.kt#L55-L88 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/ab-download-manager-before-1.11.2-arbitrary-file-write-via-start-headless-download-csrf (CNA: VulnCheck; third-party-advisory)

- https://github.com/amir1376/ab-download-manager (disclosure@vulncheck.com)

- https://github.com/amir1376/ab-download-manager/blob/v1.11.1/desktop/app/src/main/kotlin/com/abdownloadmanager/desktop/integration/IntegrationHandlerImp.kt#L55-L88 (disclosure@vulncheck.com)

- https://github.com/amir1376/ab-download-manager/blob/v1.11.1/integration/server/src/main/kotlin/com/abdownloadmanager/integration/Endpoints.kt#L27-L75 (disclosure@vulncheck.com)

- https://github.com/amir1376/ab-download-manager/commit/34cd27af6a9a6c2046af112bc9bd34828fec0bbc (disclosure@vulncheck.com)

- https://github.com/amir1376/ab-download-manager/issues/1489 (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/ab-download-manager-before-1.11.2-arbitrary-file-write-via-start-headless-download-csrf (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-121451; retrieved 2026-11-09; source updated 2026-11-09

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-121451; retrieved 2026-11-03; source updated 2026-11-03

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-121451; retrieved 2026-11-09; source updated Not reported

Revision: b42e3dd7ed14105b1548ae0bb3a8ef62258004d3edd2519c0005beb089a1d4b9

Canonical: https://y2.dev/cve/CVE-2026-121451

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- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

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