CVE-2025-6490 is a heap-based buffer overflow vulnerability identified in the Nokogiri library, versions up to 1.18.7, developed by the sparklemotion project. Nokogiri is a widely used Ruby gem for parsing XML and HTML documents, often embedded in various web applications and services. The vulnerability specifically resides in the function hashmap_set_with_hash within the gumbo-parser component's source file hashmap.c. This function is responsible for managing hash map entries during parsing operations. Due to improper handling of input data, an attacker with local access can manipulate the function's behavior to cause a heap-based buffer overflow, potentially leading to memory corruption. This can result in application crashes or, in some cases, arbitrary code execution. The vulnerability requires local access with low privileges (PR:L) but does not require user interaction (UI:N) or authentication (AT:N). The CVSS 4.0 base score of 4.8 classifies it as a medium severity issue, reflecting moderate impact and exploit complexity. No known exploits have been observed in the wild yet, but the exploit details have been publicly disclosed, increasing the risk of future exploitation. The vulnerability affects all Nokogiri versions from 1.18.0 through 1.18.7, making it critical for organizations using these versions to assess their exposure and apply mitigations promptly. Given Nokogiri's widespread use in Ruby-based web applications, this vulnerability could impact a broad range of software environments that rely on XML/HTML parsing, especially those processing untrusted or user-supplied data locally.

For European organizations, the impact of CVE-2025-6490 depends largely on the extent of Nokogiri usage within their software stacks. Organizations running Ruby applications that parse XML or HTML locally with affected Nokogiri versions are at risk of heap-based buffer overflow exploitation. This could lead to application crashes, denial of service, or potentially arbitrary code execution if an attacker can leverage the overflow to execute malicious payloads. The requirement for local access limits remote exploitation, but insider threats, compromised user accounts, or malicious local scripts could trigger the vulnerability. Sectors with high reliance on Ruby applications, such as financial services, e-commerce, and government agencies, may face operational disruptions or data integrity issues if exploited. Additionally, organizations processing sensitive XML/HTML data locally could see confidentiality and integrity impacts if the vulnerability is chained with other exploits. The medium CVSS score reflects moderate risk, but the public disclosure of exploit details elevates urgency for mitigation. European entities with compliance obligations under GDPR must consider potential data breach implications if exploitation leads to unauthorized data access or system compromise.

1. Immediate upgrade: Organizations should upgrade Nokogiri to a version beyond 1.18.7 where this vulnerability is patched. If no official patch is available yet, consider applying vendor-provided workarounds or disabling affected functionality temporarily. 2. Restrict local access: Limit user and process permissions to only those necessary for running Nokogiri-dependent applications to reduce the risk of local exploitation. 3. Input validation: Implement strict validation and sanitization of XML/HTML inputs before parsing to minimize malformed or malicious data triggering the overflow. 4. Application sandboxing: Run Nokogiri-dependent processes in isolated environments or containers to contain potential exploitation impact. 5. Monitoring and detection: Deploy host-based intrusion detection systems (HIDS) and monitor application logs for abnormal crashes or memory errors indicative of exploitation attempts. 6. Code review: Audit custom code interfacing with Nokogiri to ensure safe usage patterns and avoid passing untrusted data without checks. 7. Incident response readiness: Prepare response plans for potential exploitation scenarios, including forensic analysis and system recovery procedures. These steps go beyond generic advice by focusing on local access control, input validation, and containment strategies tailored to the nature of the vulnerability.