CVE-2026-43958: Stack Buffer Overflow in rrdcached

Technical summary

The vulnerability exists in rrdcached's request handling logic, where insufficient bounds checking on CREATE request payloads allows a stack-based buffer overflow (CWE-121). An attacker with local socket access can write beyond allocated buffer boundaries, overwriting stack memory including return addresses and saved context. This direct memory corruption can be leveraged to achieve denial of service through crash, or to construct ROP chains or shellcode payloads for code execution. The attack surface is limited to local attackers with socket connectivity, but exploitation does not require elevated privileges—a regular unprivileged user with rrdcached socket access can trigger the flaw.

Business impact

Organizations relying on rrdtool's caching layer for time-series metrics collection (including network performance monitoring, server telemetry, and infrastructure alerting) face potential service downtime if an attacker crashes rrdcached. More critically, if arbitrary code execution is achieved, an attacker could read sensitive historical data, modify metrics to mask malicious activity, or pivot to other systems. This is particularly significant in environments where rrdcached runs with service-level privileges and handles operational metrics that feed into security or SLA dashboards.

Affected systems

The vulnerability affects rrdcached components in rrdtool installations. Specific affected versions are not enumerated in available disclosures; vendors and product information was not provided. Organizations should consult rrdtool and distribution-specific security advisories to confirm which versions are vulnerable. Installations where rrdcached is exposed via socket to untrusted local users (containers, multi-tenant systems, or shared hosting) are at elevated risk.

Exploitability

Exploitation requires local socket access to rrdcached, which significantly restricts the attack surface compared to network-facing vulnerabilities. However, exploitability is straightforward once access is gained: an attacker need only craft an oversized CREATE request without special authentication or system conditions. The CVSS vector (AV:L/AC:L/PR:L) reflects low complexity—this is not a race condition or multi-step attack, but a direct trigger. In shared or containerized environments, or where rrdcached sockets are world-readable, risk is elevated. The vulnerability is not currently tracked as actively exploited in the wild (KEV status: not listed).

Remediation

Apply vendor patches to rrdtool and rrdcached as soon as they become available. Verify specific patch versions through official rrdtool security advisories and your distribution's package repositories. In parallel, implement socket access controls: restrict rrdcached socket permissions (chmod 600 or similar) to prevent unauthorized local access, and consider running rrdcached in a restricted container or namespace if feasible. Monitor rrdcached process stability for unexpected crashes or restarts.

Patch guidance

Check rrdtool's official security announcements and your system's package manager (apt, yum, apk, etc.) for patched versions addressing CVE-2026-43958. Verify patch availability through your vendor or distribution's advisory channels before deploying. Once patches are released, prioritize deployment in environments where rrdcached is exposed to multiple local users or runs in multi-tenant settings. Test patches in staging to ensure monitoring continuity.

Detection guidance

Monitor for rrdcached process crashes or unexpected restarts, which may indicate exploitation attempts or successful DoS attacks. Enable process-level monitoring and log aggregation around rrdcached startup/failure events. If available, configure rrdcached with debug or verbose logging to capture malformed requests. Host-based intrusion detection or seccomp filters can flag unusual syscall patterns (segmentation faults, memory access violations) associated with stack corruption. Review socket access logs and audit trail for unexpected connections to rrdcached sockets.

Why prioritize this

This vulnerability merits prompt attention due to its HIGH CVSS score (7.8) and the combination of confidentiality, integrity, and availability impacts. While local-only access limits the immediate attack surface, environments with untrusted local users or shared systems are at real risk. The straightforward exploitation mechanism (no special privileges required, low complexity) means that once an attacker has socket access, triggering the flaw is trivial. Organizations should prioritize patching in multi-tenant or shared infrastructure first, then proceed to standard deployments.

Risk score, explained

The CVSS 3.1 score of 7.8 (HIGH) reflects: local attack vector, low attack complexity, low privilege requirement, no user interaction, unchanged scope, but high impact across confidentiality, integrity, and availability. The stack-based buffer overflow permits both denial of service (availability) and potential code execution (confidentiality and integrity), justifying the maximum impact ratings. The score appropriately discounts the local-only requirement while emphasizing the severity of feasible outcomes.

Frequently asked questions