Hitachi Energy e-mesh EMS Vulnerable to Heap-Based Buffer Overflow
Hitachi Energy's e-mesh EMS product is affected by a critical heap-based buffer overflow vulnerability in its NGINX component, potentially leading to application outages and arbitrary code execution.
Hitachi Energy has disclosed a significant security vulnerability affecting multiple versions of its e-mesh EMS product. The flaw, identified as CVE-2026-42945, resides within the NGINX component used by the energy management system and impacts versions 4.1.6, 4.4.2, and 4.7.0.
The vulnerability is a heap-based buffer overflow that can be triggered by an unauthenticated attacker. Exploitation requires the attacker to send specifically crafted HTTP requests under certain conditions. Successful exploitation could lead to a buffer overflow in the NGINX worker process, causing the application to restart and resulting in a denial-of-service condition. More critically, in environments where Address Space Layout Randomization (ASLR) is disabled or can be bypassed, attackers may achieve arbitrary code execution.
The affected NGINX versions are v1.30.0 and below. The vulnerability specifically lies within the ngx_http_rewrite_module module when a rewrite directive is followed by another rewrite, if, or set directive, and an unnamed PCRE capture (like $1, $2) is used with a replacement string containing a question mark (?). This complex condition allows for the overflow to occur.
Hitachi Energy acknowledges the severity of this issue and recommends immediate actions for mitigation and remediation. The primary vendor fix involves applying hotfixes to update the NGINX component to at least v1.30.2 or the latest available version for the respective e-mesh EMS versions. This directly addresses the underlying NGINX vulnerability.
For organizations unable to immediately apply the vendor hotfix, several mitigation strategies are advised. These include reconfiguring rewrite rules to ensure that the ? character is not used to replace unnamed captures. Additionally, ensuring that ASLR is actively enabled (set to value 2) across all deployment targets is crucial for preventing arbitrary code execution.
Further complicating the security posture, the underlying Ubuntu Server 20.04 LTS operating system used by e-mesh EMS versions 4.1.6 and 4.4.2 is nearing its End of Life. Hitachi Energy recommends upgrading these versions to Ubuntu Server 22.04 or 24.04. As an interim measure, activating Ubuntu Pro/ESM can provide extended security maintenance.
The CVSS v3.1 score for this vulnerability is a HIGH 8.1, with a CVSS v4.0 score of CRITICAL 9.2, underscoring the significant risk it poses. CISA has also provided recommendations, urging users to minimize network exposure for control system devices, ensure they are not internet-accessible, and place them behind firewalls, isolating them from business networks. Secure remote access methods like VPNs should be used when necessary, with the caveat that VPNs themselves must be kept updated.
This advisory highlights the ongoing challenges in securing industrial control systems, where complex software components and underlying operating system lifecycles can introduce significant vulnerabilities. Prompt patching and diligent configuration management are essential to protect critical infrastructure from potential disruption and compromise.