What is the CVSS score of CVE-2026-44161?

CVE-2026-44161 has a CVSS 3.1 base score of 7.2 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:L. EPSS exploitation probability: 0.4%.

Which versions of Fluentd are affected by CVE-2026-44161?

A high-severity vulnerability in Fluentd enables attackers with control over log content to invoke arbitrary internal services, creating risk of unauthorized access to backend systems and data…. A patch is available.

How to fix or mitigate CVE-2026-44161?

Within 24 hours: identify all Fluentd instances and versions across production and development environments. Within 7 days: upgrade all deployments to Fluentd version 1.19.3 or later. Within 30 days: review audit logs for suspicious dynamic endpoint configurations and confirm strict host validation is active.

Fluentd CVE-2026-44161

HIGH

Server-Side Request Forgery (SSRF) (CWE-918)

2026-06-26 https://github.com/fluent/fluentd

GHSA-72f5-rr8c-r6gr

Authentication Bypass SSRF

7.2

CVSS 3.1 · Vendor: https://github.com/fluent/fluentd

Severity by source

Vendor (https://github.com/fluent/fluentd) PRIMARY

7.2 HIGH

AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:L

vuln.today AI

5.4 MEDIUM

Network and unauthenticated with no UI, but AC:H because exploitation requires a non-default dynamic-hostname out_http config; scope change for SSRF into other systems, limited confidentiality/availability impact, no integrity impact.

3.1 AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:N/A:L

4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:L/SI:N/SA:N

Primary rating from Vendor (https://github.com/fluent/fluentd).

CVSS VectorVendor: https://github.com/fluent/fluentd

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:L

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

Low

Integrity

None

Availability

Low

Lifecycle Timeline

Source Code Evidence Fetched

Jun 26, 2026 - 17:22 vuln.today

Analysis Generated

Jun 26, 2026 - 17:22 vuln.today

DescriptionCVE.org

The out_http output plugin allows the use of placeholders (such as ${tag}) in the endpoint configuration parameter. It was discovered that if the placeholder value is derived from untrusted user input, an attacker can maliciously control the destination hostname of the outbound HTTP requests made by Fluentd.

Impact

This vulnerability allows for a Server-Side Request Forgery (SSRF) attack. An unauthenticated attacker can force the Fluentd node to send HTTP requests to arbitrary internal services. This can lead to unauthorized access to internal APIs, data exfiltration, or the compromise of cloud metadata endpoints (e.g., AWS IMDS 169.254.169.254).

Patches

v1.19.3

Workarounds

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

Avoid Dynamic Hostnames

Do not use the placeholder in the endpoint parameter as hostname.

Restrict Network Access

Use firewall rules (e.g., iptables, AWS Security Groups) to block the Fluentd node from accessing sensitive internal IP addresses, specifically the cloud provider's metadata service and other internal microservices that Fluentd does not explicitly need to access.

Restrict allowed hosts

Inject filter to accept allowed hosts in placeholders explicitly if possible.

AnalysisAI

{tag}) whose value is derived from untrusted log data, an attacker who can influence that data forces the Fluentd node to call arbitrary internal services. There is no public exploit identified at time of analysis, but the upstream fix is shipped in v1.19.3 (PR #5394 adds strict host validation for dynamic endpoints).

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access

Identify Fluentd with dynamic out_http endpoint

Delivery

Inject crafted log event with malicious tag/record

Exploit

Placeholder expands to attacker-chosen host

Execution

Fluentd issues SSRF request to internal target

Persist

Reach cloud metadata or internal API

Impact

Exfiltrate credentials or sensitive data

Access

Identify Fluentd with dynamic out_http endpoint

Delivery

Inject crafted log event with malicious tag/record

Exploit

Placeholder expands to attacker-chosen host

Execution

Fluentd issues SSRF request to internal target

Persist

Reach cloud metadata or internal API

Impact

Exfiltrate credentials or sensitive data

Vulnerability AssessmentAI

Exploitation	Requires the out_http output plugin to be configured with a placeholder (e.g. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment	The vendor CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:L, base 7.2) presents this as network-reachable, low-complexity, unauthenticated, with a scope change reflecting that the SSRF reaches systems beyond Fluentd itself. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario	A Fluentd aggregator is configured with an out_http endpoint such as http://${tag}/ingest to dynamically route logs. An attacker submits crafted log events whose tag (or record field) resolves to 169.254.169.254, causing Fluentd to request the cloud metadata endpoint and potentially leak IAM credentials, or to reach an internal admin API otherwise unexposed. …
Remediation	Upgrade to Fluentd 1.19.3, which adds strict host validation for dynamic out_http endpoints (upstream PR https://github.com/fluent/fluentd/pull/5394); this is a tagged release, so apply Vendor-released patch: 1.19.3 as the primary fix. … Detailed patch versions, workarounds, and compensating controls in full report.