CVE-2026-44163

CVE-2026-44163 is a medium-severity allocation of resources without limits or throttling vulnerability in fluent-plugin-opentelemetry (rubygems), affecting versions <= 0.5.2. It is fixed in 0.5.3.

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Summary

fluent-plugin-opentelemetry Has Denial of Service (DoS) via Large Payloads and Decompression Bombs in in_opentelemetry

Full technical description

The fluent-plugin-opentelemetry plugin (specifically the in_opentelemetry HTTP input) lacked strict size limits on incoming requests.
It was discovered that the plugin read the entire request body and decompressed payloads into memory without enforcing maximum size thresholds.

If the OpenTelemetry ingestion endpoint is exposed to untrusted networks, an attacker can send an excessively large HTTP request or a maliciously crafted, highly compressed payload.
When the plugin attempts to read or decompress this payload, it will expand to an excessive size and it will consume significant system resources.

Workarounds

If an immediate upgrade is not possible, users are strongly advised to apply the following mitigations:

  1. Restrict Network Access
    • Ensure that the OpenTelemetry ingestion ports (default 4318) are deployed within a closed, trusted network. Use firewall rules (e.g., iptables, AWS Security Groups) to block access from untrusted networks or instances.
  2. Use a Reverse Proxy
    • If you must expose HTTP ingestion to external sources, place a robust reverse proxy (such as Nginx) in front of Fluentd. Configure the proxy to handle the gzip decompression and enforce strict limits on both compressed and uncompressed body sizes before passing the traffic to Fluentd.

Impact

This vulnerability allows for a Denial of Service (DoS) attack via memory exhaustion.
The rapid memory consumption during decompression can easily lead to an Out-of-Memory kill of the Fluentd process by the operating system.
This results in the disruption of all log collection and forwarding capabilities on the affected node.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2026-44163 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.5.3); upgrading removes the vulnerable code path.

Affected versions

fluent-plugin-opentelemetry (<= 0.5.2)

Security releases

fluent-plugin-opentelemetry → 0.5.3 (rubygems)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

v0.5.3

Frequently Asked Questions

  1. What is CVE-2026-44163? CVE-2026-44163 is a medium-severity allocation of resources without limits or throttling vulnerability in fluent-plugin-opentelemetry (rubygems), affecting versions <= 0.5.2. It is fixed in 0.5.3. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
  2. How severe is CVE-2026-44163? CVE-2026-44163 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
  3. Which versions of fluent-plugin-opentelemetry are affected by CVE-2026-44163? fluent-plugin-opentelemetry (rubygems) versions <= 0.5.2 is affected.
  4. Is there a fix for CVE-2026-44163? Yes. CVE-2026-44163 is fixed in 0.5.3. Upgrade to this version or later.
  5. Is CVE-2026-44163 exploitable, and should I be worried? Whether CVE-2026-44163 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
  6. What actually determines whether CVE-2026-44163 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
  7. How do I fix CVE-2026-44163? Upgrade fluent-plugin-opentelemetry to 0.5.3 or later.

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