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

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-11 · updated 2026-10-29
• Weakness: CWE-36

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

• WAVLINK Technology WN535M1: M35M1_V210223
• WAVLINK Technology WN535M3: M35M1_V210223

References

• https://docs.wavlink.xyz/Security_Advisory/WAVLINK-SA-2026-091301/
• https://github.com/camdsmith/wavlink-sync_server-rce/blob/main/README.md
• https://www.vulncheck.com/advisories/wavlink-wn535m1-wn535m3-unauthenticated-arbitrary-file-write-via-sync-server
• https://github.com/camdsmith/wavlink-sync_server-rce/blob/main/README.md

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