CVE-2026-79516 in stb
Summary
by MITRE • 09/09/2026
An out-of-bounds read in the stbsp_vsnprintf function (stb_sprintf.h) of nothings stb commit 31c1ad3 allows attackers to cause a Denial of Service (DoS) via sending a crafted input.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as an out-of-bounds read within the stbsp_vsnprintf function, located in the stb_sprintf.h header file from the nothings/stb library at commit 31c1ad3, represents a critical memory safety flaw that can be exploited to disrupt service availability. This specific implementation of printf-like formatting functions is widely adopted across numerous open-source projects and commercial applications due to its performance characteristics and ease of integration. The core technical defect arises from improper boundary checks during the processing of format strings or input buffers, allowing the function to read memory locations beyond the allocated buffer limits when presented with specially crafted inputs. This behavior classifies the flaw under Common Weakness Enumeration CWE-125, which describes out-of-bounds read vulnerabilities where software reads data past the end or before the beginning of the intended buffer.
From an operational perspective, while out-of-bounds reads typically result in information disclosure by leaking sensitive memory contents to the attacker, they are frequently leveraged as a mechanism for causing Denial of Service attacks. In this specific context, the exploitation likely triggers undefined behavior within the application runtime environment. Depending on the underlying architecture and compiler optimizations, such an error can lead to immediate segmentation faults, core dumps, or infinite loops if the malformed data causes subsequent logic errors in memory management routines. Attackers who can control the input passed to stbsp_vsnprintf, whether through direct API calls or via higher-level protocols that utilize this library for string formatting, can induce these crashes reliably. This effectively renders the affected application unresponsive, thereby achieving a denial of service against users relying on the compromised software component.
The attack vector aligns with ATT&CK technique T1499, Endpoint Denial of Service, specifically under sub-techniques involving resource exhaustion or crash-based methods. The vulnerability is particularly dangerous because stb libraries are often embedded statically into binaries, making patching difficult for downstream consumers who may not be aware they are using a vulnerable version of the library. Furthermore, since format string processing is common in network-facing services handling user input, such as web servers parsing headers or log files, the attack surface can be extensive if proper sanitization and validation layers are absent before invoking formatting functions.
Mitigation strategies must focus on immediate remediation through dependency updates and defensive coding practices. The primary solution involves upgrading to a patched version of the stb library where the out-of-bounds read has been corrected by adding rigorous bounds checking within the stbsp_vsnprintf implementation. Organizations should audit their codebases for direct or indirect usage of this specific function and ensure that all third-party dependencies are kept up to date with security patches provided by upstream maintainers. Additionally, implementing input validation at application boundaries is crucial; developers should verify buffer lengths and format string complexity before passing data to formatting functions. Deploying runtime protection mechanisms such as Address Sanitizer during testing phases can help detect similar memory errors early in the development lifecycle, while production environments may benefit from Web Application Firewalls or intrusion detection systems configured to identify anomalous patterns associated with fuzzed inputs targeting known vulnerable libraries.