CVE-2026-2291
Description
A heap buffer overflow was discovered in dnsmasq's DNS cache. When processing DNS responses, dnsmasq expands certain characters into longer escape sequences, but the cache buffer is not sized to hold the expanded result. A specially crafted DNS response can overflow this buffer, potentially crashing the dnsmasq process or poisoning DNS cache records.
Statement
Red Hat rates this issue as Moderate rather than Important. While DNS cache poisoning is possible, a process crash is the most likely outcome of a successful exploit. Also, standard upstream DNS resolvers reject the malformed responses before they reach dnsmasq, limiting exploitation to uncommon configurations where dnsmasq forwards directly to an attacker-controlled server.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.5 | N/A | 7.3 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | Low |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | High | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Understanding the Weakness (CWE)
Integrity,Availability,Confidentiality
Technical Impact: DoS: Crash, Exit, or Restart; Execute Unauthorized Code or Commands; Read Memory; Modify Memory
If the incorrect calculation is used in the context of memory allocation, then the software may create a buffer that is smaller or larger than expected. If the allocated buffer is smaller than expected, this could lead to an out-of-bounds read or write (CWE-119), possibly causing a crash, allowing arbitrary code execution, or exposing sensitive data.
Acknowledgements
Red Hat would like to thank Andrew Fasano (NIST) for reporting this issue.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
