Junglewise Threat Intelligence

CVE-2026-4891: dnsmasq heap out-of-bounds read in DNSSEC validation

CVE-2026-4891 · Severity: medium · CVSS 5.3 · Published 2026-05-11

Executive brief

dnsmasq is a widely used tool for providing network services like DNS and DHCP to local networks and devices. A security flaw in its DNSSEC validation component allows a remote attacker to crash the service by sending a specially crafted network packet. This results in a denial of service, preventing users and devices on the network from resolving domain names and potentially disrupting internet connectivity.

Technical details

A heap-based out-of-bounds read vulnerability exists in the DNSSEC validation logic of dnsmasq. The flaw is triggered when processing a crafted RRSIG record where the declared resource data length (rdlen) is smaller than the combined size of the fixed RRSIG header and the signer's name. This discrepancy results in a negative signature length calculation, leading to an out-of-bounds read and a subsequent process crash. The vulnerability is reachable remotely without authentication. A fix is available in dnsmasq version 2.92rel2 and has been integrated into downstream projects like Pi-hole FTL v6.6.2.

Affected products

  • dnsmasq dnsmasq < 2.92rel2
  • Red Hat Red Hat Enterprise Linux AppStream (v. 8)
  • Red Hat Red Hat Enterprise Linux AppStream (v. 9)
  • Red Hat Red Hat Enterprise Linux AppStream (v. 10)
  • Red Hat Red Hat OpenShift Container Platform 4
  • Pi-hole FTL < 6.6.2

Timeline

  • 2026-05-11: disclosed
  • 2026-05-11: patched: dnsmasq 2.92rel2 released
  • 2026-05-11: advisory: NVD published CVE-2026-4891

References

Related threats