DNS cache poisoning via undersized escape buffer
Published May 11, 2026 · Updated May 11, 2026
A heap buffer overflow in dnsmasq before 2.92rel2 allows remote attackers to poison its DNS cache or interrupt the service via DNS traffic. The extract_name() path writes escaped domain names into struct bigname, whose buffer is smaller than the required MAXDNAME*2+1 bytes. Attackers able to send DNS queries or answer forwarded queries can trigger a large heap out-of-bounds write, redirect lookups, or crash the process.
Summary
What happened
A heap buffer overflow in dnsmasq before 2.92rel2 allows remote attackers to poison its DNS cache or interrupt the service via DNS traffic. The extract_name() path writes escaped domain names into struct bigname, whose buffer is smaller than the required MAXDNAME*2+1 bytes. Attackers able to send DNS queries or answer forwarded queries can trigger a large heap out-of-bounds write, redirect lookups, or crash the process.
The record
- CVE
- CVE-2026-2291
- Published
- May 11, 2026
- Updated
- May 11, 2026
- Vendor
- Simon Kelley
- Product
- dnsmasq
- Classifications
- CWE-190, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 11, 2026CVE publishedPublication date reported by the CVE source.
- May 11, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=2.92rel2
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo