How severe is CVE-2026-44163?

CVE-2026-44163 has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-44163?

CVE-2026-44163 affects the following packages: fluent-plugin-opentelemetry (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2026-44163?

Update fluent-plugin-opentelemetry to 0.5.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44163 is resolved across your whole dependency graph.

How do I detect CVE-2026-44163 in my RubyGems dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fluent-plugin-opentelemetry, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-44163 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-44163 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-44163 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-44163?

CVE-2026-44163 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 36th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-44163?

CVE-2026-44163 is classified as CWE-409 (CWE-409). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-44163 published, and has it been updated?

CVE-2026-44163 was published on September 15, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎

💎 RubyGems

Not in CISA KEV

MEDIUM severity

CVE-2026-44163 — fluent-plugin-opentelemet…

MEDIUMFix: fluent-plugins-nursery/fluent-plugin-opentelemetry@ce6c1f2

CVE-2026-44163 is a medium-severity (CVSS 5.3) CWE-409 vulnerability in fluent-plugin-opentelemetry. A fix is available for fluent-plugin-opentelemetry — see the affected versions and patch details below.

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

Also known asGHSA-2jc5-xhx8-qj6h

Published

Sep 15, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44163.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs36th percentile — riskier than 36% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

💎fluent-plugin-opentelemetry

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

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.

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.

Patches

v0.5.3

Workarounds

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

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.
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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`fluent-plugin-opentelemetry`	all versions	0.5.3`bundle update fluent-plugin-opentelemetry --conservative`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fluent-plugin-opentelemetry, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update fluent-plugin-opentelemetry to 0.5.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44163 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

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