CVE-2026-93009
Dnsmasq: dnsmasq: heap out-of-bounds read in dhcpv6 option 39 fqdn decoder
What happened?
A flaw was found in dnsmasq. The DHCPv6 client hostname parser can read one byte past the end of a crafted FQDN option because it checks the next label length before confirming the pointer is still inside the option. An attacker on the local network can trigger this with a single DHCPv6 packet. The extra byte is not returned to the client or logged, and no crash has been demonstrated.
Affected software and versions
| Software | Version information | Fixed version |
|---|---|---|
| rhceph/alloy-rhel10Red Hat | Default status: affected | See vendor advisory |
| dnsmasqRed Hat | Default status: affected | See vendor advisory |
| dnsmasqRed Hat | Default status: affected | See vendor advisory |
| dnsmasqRed Hat | Default status: affected | See vendor advisory |
| dnsmasqRed Hat | Default status: affected | See vendor advisory |
| dnsmasqRed Hat | Default status: affected | See vendor advisory |
| openshift4/ose-baremetal-runtimecfg-rhel8Red Hat | Default status: affected | See vendor advisory |
| openshift4/ose-baremetal-runtimecfg-rhel9Red Hat | Default status: affected | See vendor advisory |
| openshift/ose-rhel-coreos-8Red Hat | Default status: affected | See vendor advisory |
| openshift/ose-rhel-coreos-9Red Hat | Default status: affected | See vendor advisory |
| openshift5/ose-baremetal-runtimecfg-rhel9Red Hat | Default status: affected | See vendor advisory |
| openshift/ose-rhel-coreos-9Red Hat | Default status: affected | See vendor advisory |
| dnsmasqRed Hat | Default status: affected | See vendor advisory |
| rhoso-operators/infra-rhel9-operatorRed Hat | Default status: affected | See vendor advisory |
Version information comes from the source record and can include unaffected products and exceptions. Distribution packages may contain backported fixes: an older upstream version alone does not prove a server is affected.
Is it being exploited?
This CVE was not listed in the CISA catalogue at our last retrieval. This does not establish that exploitation is absent.
How to respond
- Confirm the product, installed package version, and any configuration requirements in the vendor advisory.
- Follow the vendor’s remediation or workaround guidance in the references below. Structured fixed-version data is unavailable here; the publisher’s description may include a fix or workaround.
- Restart affected services if required, then verify the running version. Known exploitation may warrant investigation as well as patching.