CVE-2023-33285 in Qt
Summary
by MITRE • 05/22/2023
An issue was discovered in Qt 5.x before 5.15.14, 6.x before 6.2.9, and 6.3.x through 6.5.x before 6.5.1. QDnsLookup has a buffer over-read via a crafted reply from a DNS server.
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Analysis
by VulDB Data Team • 01/04/2026
The vulnerability identified as CVE-2023-33285 represents a critical buffer over-read flaw within the Qt framework's DNS lookup implementation. This issue affects multiple versions of the Qt library including 5.x prior to 5.15.14, 6.x prior to 6.2.9, and 6.3.x through 6.5.x prior to 6.5.1. The vulnerability specifically resides in the QDnsLookup class which is responsible for handling DNS resolution operations in Qt applications. When a Qt application utilizing QDnsLookup receives a malformed DNS response from a malicious or compromised DNS server, the application can experience a buffer over-read condition that may lead to arbitrary code execution or system instability.
The technical nature of this vulnerability stems from insufficient bounds checking within the DNS response parsing logic of QDnsLookup. When processing DNS replies, the Qt library does not properly validate the length of incoming data before attempting to read from memory buffers. This allows an attacker controlling a DNS server to craft a specially formatted response that exceeds expected buffer boundaries. The CWE-129 weakness classification applies here as this represents an insufficient validation of the length of input data before processing. The flaw manifests when the application attempts to parse DNS records that contain unexpected data lengths or malformed structures, causing the memory access to extend beyond allocated buffer limits.
From an operational perspective, this vulnerability poses significant risks to applications that rely on Qt's networking capabilities for DNS resolution. Any Qt application that performs DNS lookups using QDnsLookup is potentially vulnerable, including web browsers, network monitoring tools, and enterprise applications that depend on Qt for their user interfaces. The attack vector requires the victim to be directed to a malicious DNS server or to be subject to DNS spoofing attacks where the attacker can manipulate DNS responses. The impact extends beyond simple application crashes to potentially allow remote code execution, making this a critical security concern for systems running vulnerable Qt versions.
The mitigation strategy for CVE-2023-33285 involves upgrading to the patched versions of Qt where the buffer over-read has been addressed. Organizations should prioritize updating their Qt installations to versions 5.15.14, 6.2.9, or 6.5.1 respectively, depending on their current Qt version. Additionally, network administrators should implement DNS security measures such as DNSSEC validation and consider deploying DNS filtering solutions to prevent access to malicious DNS servers. The ATT&CK framework's T1071.004 technique of application layer protocol: DNS may be relevant here as this vulnerability exploits DNS communication channels. Organizations should also consider implementing network segmentation and monitoring to detect anomalous DNS traffic patterns that could indicate exploitation attempts. The vulnerability highlights the importance of proper input validation and memory safety practices in network protocol implementations, aligning with security best practices outlined in industry standards for secure coding and defensive programming techniques.