CVE-2026-4890: dnsmasq infinite loop in DNSSEC NSEC parsing

CVE-2026-4890 · Severity: high · CVSS 7.5 · Published 2026-05-11

dnsmasq is a widely used software component that provides network services like DNS and DHCP to local networks and embedded devices. A vulnerability in its DNS security validation (DNSSEC) allows a remote attacker to send a specially crafted network packet that causes the software to enter an infinite loop. This results in a denial of service, preventing the device from resolving domain names and effectively cutting off internet or network access for connected users.

Technologies: Pi-hole FTL, Red Hat Enterprise Linux AppStream, Simon Kelley Dnsmasq. Vendors: Pi-hole, Red Hat, Simon Kelley.

Quick answers

Is CVE-2026-4890 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-4890 being exploited in the wild.
How severe is CVE-2026-4890?
High severity, with a CVSS score of 7.5, published 11 May 2026.
Which products and versions are affected?
Pi-hole FTL < 6.6.2; Simon Kelley Dnsmasq versions prior to 2.92rel2.
Is there a fix for CVE-2026-4890?
A patch was published on 2026-05-11: dnsmasq 2.92rel2 released with fixes Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-4890 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-4890?
Check whether you run Pi-hole FTL, Red Hat Enterprise Linux AppStream or Simon Kelley Dnsmasq at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A Denial of Service vulnerability exists in the DNSSEC validation logic of dnsmasq due to an infinite loop during NSEC bitmap parsing (CWE-835). The root cause is a window-iteration step that omits a 2-byte window header; when a crafted NSEC record with a bitmap_length of zero is processed, the software fails to exit the loop. This vulnerability is reachable before RRSIG validation, meaning an attacker does not need to provide valid cryptographic signatures to trigger the flaw. A remote, unauthenticated attacker can exploit this by sending a single crafted DNS packet, causing dnsmasq to stop responding to all queries. The issue is resolved in dnsmasq version 2.92rel2 and 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)
  • Pi-hole Pi-hole FTL < 6.6.2

Timeline

  • 2026-05-11: disclosed: Coordinated disclosure of six CVEs by CERT/CC and Simon Kelley
  • 2026-05-11: patched: dnsmasq 2.92rel2 released with fixes
  • 2026-05-11: advisory: NVD publication date

References

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