OpenWrt odhcpd up to 25.12 DHCPv6 Self-Loop Detection dhcpv6.c memcmp stack-based overflow

Summaryinfo

A vulnerability identified as critical has been detected in OpenWrt odhcpd up to 25.12. This affects the function memcmp of the file dhcpv6.c of the component DHCPv6 Self-Loop Detection. This manipulation causes stack-based overflow. This vulnerability is tracked as CVE-2026-55606. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability classified as critical was found in OpenWrt odhcpd up to 25.12. Affected by this vulnerability is the function memcmp of the file dhcpv6.c of the component DHCPv6 Self-Loop Detection. The manipulation with an unknown input leads to a stack-based overflow vulnerability. The CWE definition for the vulnerability is CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. In versions 25.12 and prior, odhcpd's DHCPv6 self-loop detection at dhcpv6.c:720 uses a network-byte-order DUID length value directly as the memcmp() size parameter. On little-endian hosts, this causes memcmp() to read far beyond the stack buffer — a single unauthenticated DHCPv6 packet triggers a 2560-byte overread from a 128-byte buffer. At time of publication, there are no publicly available patches.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-55606 since 06/17/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/23/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Vendor

• OpenWrt

Name

• odhcpd

Version

• 25.0
• 25.1
• 25.2
• 25.3
• 25.4
• 25.5
• 25.6
• 25.7
• 25.8
• 25.9
• 25.10
• 25.11
• 25.12

Website

• Product: https://github.com/openwrt/odhcpd/

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