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Critical · 9.8 Public exploit CVE-2026-53921 EUVD-2026-108966

odhcpd: Stack buffer overflow in DHCPv6 IA reply serialization (2 independent sites)

Published Oct 23, 2026 · Updated Oct 29, 2026 · Assigned by GitHub_M

Vendor: openwrt Product: odhcpd

Description

odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. Prior to version 25.12, odhcpd's DHCPv6 IA response handler writes past the end of a fixed 512-byte stack buffer (pdbuf) when a single DHCPv6 REQUEST carries enough IA options to nearly exhaust the reply space. Two independent overflow sites exist in the same call chain, both reachable from the network via a single unauthenticated UDP packet. odhcpd runs as root on OpenWrt; embedded targets often lack stack canaries and ASLR, making code execution realistic. This issue has been patched in version 25.12.

Affected products

VendorProductAffectedFixed
openwrt odhcpd < 25.12 —

Public exploits

Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.

Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.

GitHub 2 repositories

  • tc4dy/CVE-2026-53921-PoC-Exploit ★ 6 · Jul 28, 2026

    CVE-2026-53921 – odhcpd Stack Overflow (CVSS 9.8) Vuln detailed and comprehensive Write-Up and Verifier & Multi-exploit for OpenWrt DHCPv6 RCE. Dual-vector (IA_NA/IA_PD) overflow with MIPS/ARM shellc…

  • ashrafzaryouh/CVE-2026-53921 ★ 2 · Jul 28, 2026

    CVE-2026-53921

Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.

References