Improper access control in Wasmtime - CVE-2026-47261
Published: May 22, 2026
Vulnerability identifier: #VU132132
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-47261
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Bytecode Alliance
Affected software:
Wasmtime
Wasmtime
Detailed vulnerability description
The vulnerability allows a remote attacker to modify file contents despite configured write restrictions.
The vulnerability exists due to improper access control in Dir::open_at when handling path_open or descriptor.open-at requests with the OpenFlags::TRUNCATE flag. A remote attacker can open a file with the truncate flag but without write permissions to modify file contents despite configured write restrictions.
Only embeddings that grant directory mutation permissions while restricting file permissions to read-only are affected.
How to mitigate CVE-2026-47261
Install security update from vendor's website.