CVE-2026-93006

A flaw was found in dnsmasq. The TFTP server can serve the wrong file contents because a recently used transfer cache is not invalidated when a transfer finishes. An attacker on the local network who can request a TFTP file may cause a later client to receive previously cached data instead of the requested file. In PXE network-boot environments this can substitute attacker-chosen boot content for a victim machine.

This vulnerability is rated as Important because cache confusion can substitute PXE boot content, with high integrity and confidentiality impact. Attack vector is adjacent network (TFTP is a LAN service) and attack complexity is high: DNS forwarding overwrites the TFTP cache key, heap reuse of the freed transfer struct is required, and TFTP option negotiation (OACK) clears the cache. Mixed DNS/TFTP deployments are much harder to exploit. TFTP-only PXE servers with DNS disabled are the highest-risk configuration. Current Red Hat dnsmasq packages ship 2.90 or earlier and do not contain the v2.92 TFTP prefetch cache. Products that later ship dnsmasq 2.92 or newer with TFTP compiled in may be affected when TFTP is enabled at runtime.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

The following measures reduce risk:

1. If TFTP is not required, do not enable it. Remove --enable-tftp from the dnsmasq configuration.
2. If TFTP is required, restrict it with --tftp-interface=<interface> and avoid running TFTP-only instances that serve untrusted clients on the same network.
3. Compile without TFTP support using COPTS=-DNO_TFTP if TFTP is not needed.