Critical severity · published Sep 10, 2026
CVE-2026-88899
knowns before 0.31.0 External Control of Agent Working Directory via x-opencode-directory Header
9.8
CVSS
0.8%
EPSS
No
On KEV
Description
knowns versions before 0.31.0 fail to properly validate the x-opencode-directory request header in the /api/opencode proxy endpoint. Remote attackers can supply arbitrary directory paths to execute file operations outside the project root on the host system.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.8% · higher than 57% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
KN
knowns · knowns-dev
before 0.31.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-88899
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-88899
github.com
https://github.com/knowns-dev/knowns/blob/v0.30.0/internal/server/server.go#L1283-L1296
github.com
https://github.com/knowns-dev/knowns/commit/37db0561b37b48b8bd035a417d7f1da6258ae657
github.com
https://github.com/knowns-dev/knowns/releases/tag/v0.31.0
github.com
https://github.com/knowns-dev/knowns/security/advisories/GHSA-9h2q-r9fh-f98w
www.vulncheck.com
https://www.vulncheck.com/advisories/knowns-before-0.31.0-external-control-of-agent-working-directory-via-x-opencode-directory-header
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