CVE-2026-55557Hinoki check available

Arbitrary file write via unconfined MCP paths

Published Aug 25, 2026 · Updated Aug 25, 2026

Path traversal in That1Drifter browse-mcp before 0.8.2 allows attackers to write arbitrary files through caller-controlled MCP paths. The browser_download tool joins an unchecked save_dir with a fetched filename, while state tools accept explicit paths unchanged. A malicious MCP client or prompt-steered agent can write response bytes anywhere the process can reach, enabling startup-file execution.

CVSS severity8.6
High
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Path traversal in That1Drifter browse-mcp before 0.8.2 allows attackers to write arbitrary files through caller-controlled MCP paths. The browser_download tool joins an unchecked save_dir with a fetched filename, while state tools accept explicit paths unchanged. A malicious MCP client or prompt-steered agent can write response bytes anywhere the process can reach, enabling startup-file execution.

The record

CVE
CVE-2026-55557
Published
Aug 25, 2026
Updated
Aug 25, 2026
Vendor
That1Drifter
Product
browse-mcp
Classifications
CWE-22, T1105
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.8.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

That1Drifter · browse-mcpversion=< 0.8.2

Published CVSS scores

8.6GitHubCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1105Ingress Tool Transfer

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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