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CVE-2026-55557— browse-mcp: Arbitrary file write via unconfined download and state paths

Quick assessment

Affected
That1Drifter browse-mcp
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Roger Maxwell browse-mcp是Roger Maxwell个人开发者的一个浏览器交互的模型上下文协议服务。 Roger Maxwell browse-mcp 0.8.2之前版本存在路径遍历漏洞，该漏洞源于browser_download、browser_save_state和browser_load_state未验证调用者控制的路径，且force_fetch绕过来源限制，可能导致攻击者向任意路径写入文件并执行主机代码。

CVSS 8.6 · High EPSS 0.24% · P14

Affected Version Matrix 1

VendorProduct Version RangeStatus
That1Drifter browse-mcp < 0.8.2 affected
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I. Basic Information for CVE-2026-55557

Vulnerability Information
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Vulnerability Title
browse-mcp: Arbitrary file write via unconfined download and state paths
Source: CVE Program / CVE List V5
Vulnerability Description
browse-mcp is a Playwright-based headless-browser MCP server for MCP-capable agents. Prior to 0.8.2, browser_download writes a fetched response body to join(save_dir, filename) without validating the caller-controlled save_dir, while browser_save_state and browser_load_state honor a caller-controlled path unchanged. A malicious MCP client, or an autonomous agent steered by indirect prompt injection on a visited page, can choose an arbitrary save_dir or state path and a URL whose response body becomes attacker-controlled file contents, allowing writes to any path the process can reach, including ~/.bashrc, autostart entries, or cron files, and potentially leading to host code execution. The force_fetch fallback also uses a raw fetch() that bypasses the BROWSE_MCP_ALLOWED_ORIGINS origin fence. This issue is fixed in version 0.8.2.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
对路径名的限制不恰当(路径遍历)
Source: CVE Program / CVE List V5
Vulnerability Title
Roger Maxwell browse-mcp 路径遍历漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Roger Maxwell browse-mcp是Roger Maxwell个人开发者的一个浏览器交互的模型上下文协议服务。 Roger Maxwell browse-mcp 0.8.2之前版本存在路径遍历漏洞，该漏洞源于browser_download、browser_save_state和browser_load_state未验证调用者控制的路径，且force_fetch绕过来源限制，可能导致攻击者向任意路径写入文件并执行主机代码。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
That1Drifter browse-mcp < 0.8.2 -

II. Public POCs for CVE-2026-55557

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Reproduced successfully in a real sandbox · Below is the actual recording of building the environment and exploiting the vulnerability.
Success marker: VULNERABLE: arbitrary file write outside download root — token PROOF_6146d922968de4be recovered from /tmp/steal.txt (browser_download save_dir=/tmp honored an absolute path)
Reproduction recording is a Pro+ exclusive
Watch the full sandbox build + live exploit recording for this CVE. Limited-time ¥499/mo.
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claude_code · 8305 chars
GitHub 复现环境（可 clone 直接跑）
Pro+ exclusive includes:
Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
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Trigger conditions & impact
Full executable POC code
Exploit chain & mitigation
POC zip download
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III. Intelligence Information for CVE-2026-55557

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Patches & Fixes for CVE-2026-55557 (3)

Vendor Advisories for CVE-2026-55557 (2)

IV. Related Vulnerabilities

Same weakness: CWE-22

V. Comments for CVE-2026-55557

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