CVE-2026-88899Public exploitNetwork attack vector

Host file access and manipulation via header preservation

Published Sep 10, 2026 · Updated Sep 10, 2026

Path traversal in Knowns before 0.31.0 allows remote attackers to read or alter host files via crafted proxy requests. proxyOpenCode preserves a nonempty x-opencode-directory header or directory query value and forwards it as the OpenCode daemon's working directory instead of replacing it with activeRoot. Reachability requires HTTP access to the Knowns server and an active OpenCode runtime; operations run with the daemon process's file and tool privileges.

CVSS severity9.3
Critical
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Path traversal in Knowns before 0.31.0 allows remote attackers to read or alter host files via crafted proxy requests. proxyOpenCode preserves a nonempty x-opencode-directory header or directory query value and forwards it as the OpenCode daemon's working directory instead of replacing it with activeRoot. Reachability requires HTTP access to the Knowns server and an active OpenCode runtime; operations run with the daemon process's file and tool privileges.

The record

CVE
CVE-2026-88899
Published
Sep 10, 2026
Updated
Sep 10, 2026
Vendor
Knowns
Product
Knowns
Classifications
CWE-73, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 10, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=0 <0.31.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Knowns · Knownsversion=0 <0.31.0

Published CVSS scores

9.3VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
9.8VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
10.0knowns-devCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-73External Control of File Name or Path
T1190Exploit Public-Facing Application

Public exploit references

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo