CVE-2026-26931: 
Kibana vulnerability analysis and mitigation

CVE-2026-26931 is a Memory Allocation with Excessive Size Value (CWE-789) vulnerability in the Prometheus remote_write HTTP handler within Elastic Metricbeat. It allows a low-privileged attacker on an adjacent network to trigger excessive memory allocation, resulting in a Denial of Service (DoS) condition. The vulnerability affects Metricbeat versions 8.0.0 through 8.19.12, as well as the Go module github.com/elastic/beats/v7 prior to version 7.0.0-alpha2.0.20260112100137-de072c4e371e. It was published on March 19, 2026, with a CVSS v3.1 base score of 5.7 (Medium) (GitHub Advisory, Elastic Advisory).

The root cause is classified as CWE-789 (Memory Allocation with Excessive Size Value), where the Prometheus remote_write HTTP handler in Metricbeat allocates memory based on an untrusted, user-controlled size value without enforcing appropriate upper bounds. An attacker with low privileges on an adjacent network can send specially crafted HTTP requests to this handler, causing the application to allocate arbitrarily large amounts of memory. The attack pattern is categorized as CAPEC-130 (Excessive Allocation), and exploitation requires no user interaction. No public proof-of-concept code has been identified (GitHub Advisory, Elastic Advisory).

Successful exploitation results in resource exhaustion on the affected Metricbeat instance, causing a Denial of Service that renders the monitoring agent unavailable. There is no impact on confidentiality or data integrity — the vulnerability is limited to availability. Affected deployments running Metricbeat versions 8.0.0 through 8.19.12 in environments where the Prometheus remote_write endpoint is accessible to adjacent network peers are at risk (GitHub Advisory, Elastic Advisory).

There is no public proof-of-concept exploit and no evidence of active in-the-wild exploitation as of the time of publication. The EPSS score is approximately 0.015–0.022%, placing it in the 6th percentile for exploitation likelihood within 30 days. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. Exploitation requires low privileges and adjacent network access, limiting the attack surface compared to remotely exploitable vulnerabilities (GitHub Advisory).

• Network: Unusual or high-volume HTTP POST requests to the Metricbeat Prometheus remote_write endpoint from unexpected adjacent network sources.
• Logs: Metricbeat logs showing repeated large or malformed requests to the remote_write handler; out-of-memory (OOM) errors or crash reports in Metricbeat service logs.
• Process: Sudden spike in memory consumption by the Metricbeat process leading to process termination or system-level OOM killer events.
• System: Unexpected Metricbeat service restarts or availability gaps in metrics collection pipelines.

Elastic has released Metricbeat version 8.19.13 (and 9.2.5 for the 9.x branch) to address this vulnerability; users should upgrade immediately (Elastic Advisory). For the Go module, the patched version is 7.0.0-alpha2.0.20260112100137-de072c4e371e (GitHub Advisory). As a workaround, restrict network access to the Prometheus remote_write HTTP handler to trusted sources only, implement network segmentation to limit adjacent network exposure, and apply resource limits (e.g., memory cgroups) on systems running Metricbeat to reduce the impact of excessive allocation.

Elastic published a security advisory (ESA-2026-09) on March 19, 2026, disclosing the vulnerability and providing patched versions (Elastic Advisory). The vulnerability was also catalogued by ENISA (EUVD-2026-13139) and tracked by multiple vulnerability aggregators. No notable independent researcher commentary or significant social media discussion has been identified beyond standard CVE tracking activity.