An OS buffer overflow vulnerability exists in the Tenda W20E model, firmware V4.0br, specifically at firmware build 15.11.0.6. The flaw arises because the parameter pPortMapIndex is not validated before being copied into a fixed-size buffer with strcpy, a classic out‑of‑bounds memory write. This weakness permits an attacker who can supply malformed input to overwrite adjacent memory, potentially causing a crash or executing arbitrary code on the device. The vulnerability is coded as CWE‑120, reflecting an unsafe string handling operation. The impact is the loss of data integrity and confidentiality, with the possibility of remote code execution if the attacker controls the input source.

The affected device is the Tenda W20E router, running firmware V4.0br, build 15.11.0.6. No other vendors or product versions are specified. Consequently, only deployments of this exact router model and firmware version are directly susceptible to the flaw.

The vulnerability carries a CVSS v3 base score of 7.5, indicating high severity. EPSS indicates an exploitation probability of less than 1 %. The flaw is not listed in CISA’s KEV catalog, suggesting that known exploits are scarce or have not been observed in the wild. Based on the description, the likely attack vector is remote, via the router’s web management interface or API that accepts the pPortMapIndex parameter. An attacker would need to send a crafted input longer than the buffer, which may be achievable through a simple HTTP request. The lack of an official patch or workaround is noted; therefore, the risk remains high until a firmware update becomes available.