WAVLINK-SA-2026-091301: Arbitrary File Write in WN535M1
Abstract
WAVLINK WN535M1 and WN535M3 routers running firmware prior to M35M1_V250922 contain an unauthenticated arbitrary file write vulnerability that allows remote attackers to overwrite any file on the device by sending a crafted payload to the sync_server daemon on TCP port 13136. The daemon, which runs as root and requires no authentication, accepts a 100-byte filename field in its protocol header without path canonicalization, allowing attackers to supply an absolute path and write arbitrary content to overwrite startup scripts or credential stores to achieve persistent system compromise. This vulnerability was reported together with CVE-2026-89010 (unauthenticated OS command injection in the same sync_server daemon on TCP port 13136); both issues affect the same models and are addressed by the same firmware release.
Affected Products
| Product | Affected Firmware | Fixed Firmware | Availability |
|---|---|---|---|
| WN535M1 Wi-Fi Router | Prior to M35M1_V250922 and earlier |
M35M1_V250922 or later |
Available now · Download |
Detail
WAVLINK WN535M1 and WN535M3 routers running firmware prior to M35M1_V250922 contain an unauthenticated arbitrary file write vulnerability that allows remote attackers to overwrite any file on the device by sending a crafted payload to the sync_server daemon on TCP port 13136. The daemon, which runs as root and requires no authentication, accepts a 100-byte filename field in its protocol header without path canonicalization, allowing attackers to supply an absolute path and write arbitrary content to overwrite startup scripts or credential stores to achieve persistent system compromise. This vulnerability was reported together with CVE-2026-89010 (unauthenticated OS command injection in the same sync_server daemon on TCP port 13136); both issues affect the same models and are addressed by the same firmware release. Tracked as CVE-2026-89009 · CVSS v3.1 9.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H)
Solution
Update the firmware to version M35M1_V250922 or later or later.
Acknowledgement
Thanks to Cam Smith for reporting this vulnerability.
Reference
CVE-2026-89009 · NVD entry