Vulnerability · Published Sep 11, 2026 · Assigned by VulnCheck

CVE-2026-89009WAVLINK WN535M1/WN535M3 Unauthenticated Arbitrary File Write via sync_server

Critical 9.1

In plain English

A critical-severity security flaw in WN535M1 from WAVLINK Technology. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 1.0% (higher than 63% of all known vulnerabilities).

Severity (CVSS 3.1)9.1Critical

Exploit odds (30 days)1.0%top 36.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

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.

Affected products (as reported)

Vendor	Product	Versions
WAVLINK Technology	WN535M1	M35M1_V210223
WAVLINK Technology	WN535M3	M35M1_V210223

Weakness: CWE-36 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

References

Researcher Disclosure technical-description, exploit
WAVLINK Advisory patch, vendor-advisory
https://www.vulncheck.com/advisories/wavlink-wn535m1-wn535m3-unauthenticated-arbitrary-file-write-via-sync-server third-party-advisory