DNSdist Memory Allocation Vulnerabilities

dnsdist can be forced into excessive memory allocation when a client generates high volumes of DNS queries routed to an overloaded DNS-over-HTTPS (DoH) backend, causing queries to accumulate in an unbounded buffer that persists until connection closure. This denial-of-service condition affects dnsdist deployments with DoH backends under load, allowing unauthenticated remote attackers to exhaust server memory with sustained query traffic.

DNSdist allows remote attackers to create unlimited concurrent DoQ (DNS over QUIC) or DoH3 (DNS over HTTPS/3) connections, triggering unbounded memory allocation and denial of service. The vulnerability affects configurations where these protocols are explicitly enabled, as both are disabled by default. No authentication is required for exploitation, and CVSS 5.3 (AC:L, AV:N) indicates straightforward network-based triggering under default conditions.

dnsdist allows remote denial-of-service attacks through memory exhaustion by generating numerous error responses on single DoQ (DNS-over-QUIC) and DoH3 (DNS-over-HTTPS/3) connections. An unauthenticated remote attacker can trigger excessive memory allocation by rapidly sending queries that produce error responses, with resources not properly released until connection termination. CVSS 5.3 (AV:N/AC:L/PR:N/UI:N) reflects network-accessible availability impact; no public exploit identified at time of analysis.