A heap-based buffer overflow vulnerability exists in openNDS before 11.0.0 that allows an unauthenticated attacker on the captive portal network to… (CVE-2026-38821)

CVE-2026-38821 is a heap-based buffer overflow vulnerability in openNDS prior to version 11.0.0. An unauthenticated attacker with access to the captive portal network can exploit this flaw to crash the openNDS daemon, resulting in denial of service, and may also achieve remote code execution. The issue is specifically in the http_microhttpd.c source file. The vulnerability has a CVSS 3.1 base score of 7.1, indicating high severity, with attack vector as adjacent network, high attack complexity, no privileges required, no user interaction, unchanged scope, and high impact on confidentiality and integrity, with low impact on availability.

Successful exploitation can lead to denial of service by crashing the openNDS daemon and may allow remote code execution, compromising confidentiality and integrity of the system. The attacker does not require authentication but must be on the captive portal network. The vulnerability poses a high security risk due to potential remote code execution.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided in the available data. Until a patch is available, restrict access to the captive portal network and monitor for suspicious activity related to openNDS.