Dnsmasq: dnsmasq: tcp/53 child-slot exhaustion starves dnssec validation
Summary
| CVE | CVE-2026-93007 |
|---|---|
| State | PUBLISHED |
| Assigner | redhat |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-29 13:17:15 UTC |
| Updated | 2026-10-30 08:17:00 UTC |
| Description | A flaw was found in dnsmasq. The TCP DNS service uses a small fixed pool of child processes and does not set a receive timeout on client connections. A remote attacker can open idle TCP connections to port 53 and occupy the entire pool, preventing new TCP DNS connections and DNSSEC validation that requires TCP fallback. UDP DNS resolution continues, and occupied slots are released after a fixed lifetime. |
Risk And Classification
Primary CVSS: v3.1 5.3 MEDIUM from [email protected]
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Problem Types: CWE-400 | CWE-400 Uncontrolled Resource Consumption
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 5.3 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| 3.1 | CNA | CVSS | 5.3 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
NoneAvailability
LowCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| access.redhat.com/security/cve/CVE-2026-93007 | [email protected] | access.redhat.com | |
| bugzilla.redhat.com/show_bug.cgi | [email protected] | bugzilla.redhat.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Red Hat would like to thank Shubham Raj (Causal Security) for reporting this issue. (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-09-14T00:00:00.000Z | Reported to Red Hat. |
| CNA | 2026-10-28T09:32:00.000Z | Made public. |
Workarounds
CNA: The following measures reduce risk: 1. Increase the TCP connection limit with --max-tcp-connections=<N> to raise the number of connections an attacker must hold. 2. Limit per-source TCP connections to port 53 with firewall rules, for example iptables connlimit on tcp/53. 3. Restrict which hosts can reach TCP port 53 if TCP DNS is not required from untrusted networks.
There are currently no legacy QID mappings associated with this CVE.