CVE-2026-110656 in miniupnpc
Summary
by MITRE • 10/15/2026
miniupnpc through 2.3.3 contains a one-byte heap out-of-bounds read vulnerability in the minixml parseelt function's namespace-prefix handling that skips an end-of-buffer check after advancing past ':'. A malicious or spoofed UPnP gateway on the local network can send a device description or SOAP reply ending in ':' within an element name to crash the client.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified in miniupnpc versions through 2.3.3 represents a critical memory safety flaw rooted in improper boundary validation during XML parsing operations. Specifically, the defect resides within the minixml parseelt function, which is responsible for processing element names and handling namespace prefixes. When the parser encounters a colon character that signifies the separation between a namespace prefix and the local part of an element name, it advances its internal pointer past this delimiter to continue processing the remainder of the string. However, in certain edge cases where the input data ends immediately after or near this delimiter, the code fails to perform a necessary end-of-buffer check before attempting to access subsequent memory locations. This oversight results in a one-byte heap out-of-bounds read, allowing the application to retrieve uninitialized or arbitrary data from adjacent memory regions rather than safely terminating the parsing process upon reaching the string's terminus.
From an operational perspective, this vulnerability poses a significant risk to devices and applications that rely on miniupnpc for Universal Plug and Play (UPnP) functionality. UPnP is commonly used in home routers, media servers, and IoT devices to facilitate automatic port forwarding and service discovery without manual configuration. Because the flaw can be triggered by sending specifically crafted XML data containing an element name ending with a colon, it creates a vector for denial-of-service attacks against local network clients. A malicious actor or a compromised spoofed UPnP gateway on the same local area network can exploit this condition to cause the miniupnpc client application to crash due to invalid memory access. This disruption not only affects the availability of the specific application but may also destabilize broader network connectivity if the affected software is integral to system operations, such as automatic port mapping for gaming consoles or streaming devices.
The technical classification of this issue aligns with CWE-125, which defines out-of-bounds read vulnerabilities where a program reads data beyond the intended buffer boundary. In the context of modern attack frameworks, this vulnerability maps to MITRE ATT&CK technique T1498.002, Network Denial of Service via Resource Exhaustion by Local Exploitation. The attacker leverages local network access to send malformed UPnP device descriptions or SOAP replies that trigger the memory error in the client-side parser. While the immediate impact is typically a crash rather than arbitrary code execution due to the read-only nature of the flaw, such instability can be chained with other vulnerabilities or used as part of a broader reconnaissance and disruption campaign against networked devices. The lack of robust input validation on namespace prefixes highlights a common oversight in legacy XML parsing libraries where performance optimizations sometimes bypass strict boundary checks under the assumption that well-formed data will always be provided by trusted sources, an assumption that fails in hostile local network environments.
Mitigation strategies for this vulnerability primarily involve updating miniupnpc to version 2.3.4 or later, where the developers have implemented proper bounds checking within the parseelt function to ensure that pointer advancement does not exceed buffer limits when processing namespace prefixes. For organizations unable to immediately patch affected systems, defensive measures include isolating UPnP traffic from untrusted networks and disabling UPnP services on devices where automatic port mapping is not strictly required. Network segmentation can also limit exposure by ensuring that only trusted gateways are allowed to communicate with client applications using miniupnpc. Additionally, deploying intrusion detection signatures capable of identifying malformed XML structures containing anomalous namespace delimiters at the end of element names may provide an additional layer of defense against exploitation attempts from spoofed or malicious UPnP endpoints on the local network.