CVE-2026-112300 in configobj
Summary
by MITRE • 10/20/2026
A vulnerability was identified in DiffSK configobj up to 5.0.9. Affected by this vulnerability is the function _sectionmarker of the file configobj/__init__.py. The manipulation leads to inefficient regular expression complexity. Remote exploitation of the attack is possible. The project was informed of the problem early through an issue report but has not responded yet.
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Analysis
by VulDB Data Team • 10/20/2026
The identified security flaw resides within the DiffSK fork of the ConfigObj library, specifically affecting versions up to 5.0.9. This vulnerability centers on a critical implementation error in the sectionmarker function located in the configobj/__init_.py module. The core technical issue is characterized by inefficient regular expression complexity, which introduces significant performance degradation when processing certain inputs. While many configuration parsers are designed for local file reading and thus primarily face risks related to resource exhaustion via large files, this specific implementation allows for remote exploitation scenarios where an attacker can trigger the flawed logic through network-accessible interfaces that parse untrusted configuration data.
From a technical perspective, the vulnerability is classified under CWE-400, which denotes Uncontrolled Resource Consumption. The inefficient regular expression likely suffers from catastrophic backtracking or excessive complexity in its pattern matching algorithm. When such regex patterns are applied to specially crafted input strings, they can consume disproportionate amounts of CPU cycles and memory relative to the size of the input data. This behavior effectively creates a Denial of Service condition by exhausting system resources, potentially causing the application hosting ConfigObj to become unresponsive or crash entirely. The lack of proper bounds checking or optimization in the regex engine allows an adversary to craft payloads that maximize computational overhead without requiring large file sizes, making it particularly dangerous in high-throughput environments.
The operational impact of this vulnerability is severe for any service relying on ConfigObj to parse configuration files received over a network. If an application exposes endpoints that accept user-supplied data which is subsequently parsed using the vulnerable version of ConfigObj, attackers can leverage this flaw to disrupt service availability. This aligns with ATT&CK technique T1499, Endpoint Denial of Service, specifically under sub-techniques related to resource exhaustion via software vulnerabilities. The ability to remotely exploit this issue means that even if the configuration data is not directly executed as code, its mere parsing can serve as a vector for disrupting critical infrastructure or application services.
Although the project maintainers were notified early through an official issue report, there has been no public response or patch release addressing this specific flaw in versions up to 5.0.9. Consequently, organizations currently utilizing these affected versions remain exposed to potential denial-of-service attacks via malformed configuration inputs. Immediate mitigation strategies should include upgrading to a patched version of ConfigObj once available from the DiffSK repository or an alternative maintained fork that addresses regex efficiency issues. In the interim, deploying web application firewalls with rules capable of detecting and blocking excessively complex regular expression patterns in input fields can provide a layer of defense. Additionally, implementing strict rate limiting and resource quotas for configuration parsing endpoints can help mitigate the impact of such attacks by preventing any single request from monopolizing system resources indefinitely.