CVE-2025-5890 is a vulnerability identified in version 0.5.0 of the 'actions toolkit' product, specifically within the 'globEscape' function located in the file toolkit/packages/glob/src/internal-pattern.ts. The vulnerability arises due to inefficient regular expression complexity, which can be exploited remotely without user interaction or authentication. This inefficiency can lead to excessive CPU consumption when processing specially crafted input, resulting in a denial-of-service (DoS) condition. The vulnerability is classified as 'problematic' with a CVSS 4.0 base score of 5.3 (medium severity), indicating a moderate risk. The attack vector is network-based (AV:N), requires low attack complexity (AC:L), no privileges (PR:L) but no user interaction (UI:N), and impacts availability with low impact (VA:L). The vulnerability does not affect confidentiality or integrity. No known exploits are currently reported in the wild, and no patches or mitigations have been linked yet. The root cause is the inefficient handling of regular expressions in the globEscape function, which can be triggered remotely, potentially allowing attackers to degrade service performance or cause application unavailability by triggering resource exhaustion through crafted input patterns.

For European organizations, the primary impact of CVE-2025-5890 is the risk of denial-of-service attacks against systems using the vulnerable version of the actions toolkit. This can lead to service disruptions, degraded application performance, and potential downtime. Organizations relying on automation workflows, CI/CD pipelines, or other tooling that incorporates this toolkit may experience interruptions, affecting development velocity and operational stability. While the vulnerability does not directly compromise data confidentiality or integrity, availability impacts can have downstream effects on business continuity and service level agreements. Industries with high reliance on automated development and deployment tools, such as financial services, telecommunications, and critical infrastructure sectors in Europe, may face operational risks. Additionally, the remote exploitability without user interaction increases the threat surface, especially for externally exposed services or APIs that process glob patterns using the affected toolkit. The absence of known exploits reduces immediate risk but does not eliminate the potential for future attacks once exploit code becomes available.

European organizations should first identify any usage of actions toolkit version 0.5.0 within their software stacks, particularly in CI/CD pipelines, automation scripts, or any tooling that processes glob patterns. Immediate mitigation involves upgrading to a patched version once available from the vendor or applying any official patches addressing the inefficient regex complexity. In the absence of patches, organizations can implement input validation and sanitization to restrict or reject suspicious glob pattern inputs that could trigger excessive regex processing. Rate limiting and resource usage monitoring on services utilizing the toolkit can help detect and mitigate potential abuse attempts. Additionally, isolating vulnerable components behind firewalls or network segmentation can reduce exposure. Security teams should monitor threat intelligence feeds for exploit developments and apply timely updates. Incorporating anomaly detection for unusual CPU or memory usage spikes related to regex processing may provide early warning of exploitation attempts.