CVE-2026-86541Public exploitNetwork attack vector

Arbitrary file overwrite via unchecked replacement path

Published Sep 7, 2026 · Updated Sep 10, 2026

Path traversal in Knowns before 0.30.0 allows remote attackers to overwrite arbitrary host files through the code.replace MCP action. The handleCodeReplace function accepts absolute paths unchanged or joins relative paths to the project root without checking the resolved path before os.WriteFile replaces the target. The Knowns MCP server must be running and reachable, and access through a direct client or a prompt-injected LLM agent is required.

CVSS severity7.2
High
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in Knowns before 0.30.0 allows remote attackers to overwrite arbitrary host files through the code.replace MCP action. The handleCodeReplace function accepts absolute paths unchanged or joins relative paths to the project root without checking the resolved path before os.WriteFile replaces the target. The Knowns MCP server must be running and reachable, and access through a direct client or a prompt-injected LLM agent is required.

The record

CVE
CVE-2026-86541
Published
Sep 7, 2026
Updated
Sep 10, 2026
Vendor
Knowns
Product
Knowns
Classifications
CWE-863, CWE-22, T1565.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 7, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 10, 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 <0.30.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Knowns · Knownsversion=0 <0.30.0

Published CVSS scores

8.8Knowns GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
8.3VulnCheck CNACVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:H
7.2VulnCheck CNACVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

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

Weakness, pattern, technique

CWE-863Incorrect Authorization
CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1565.001Stored Data Manipulation

Public exploit references

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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