CVE-2026-44161 Fluentd: Server-Side Request Forgery (SSRF) via Placeholder Expansion in `out_http`
Attackers can exploit placeholder expansion in the out_http plugin to force Fluentd to send requests to arbitrary internal services, enabling SSRF attacks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-44161?
CVE-2026-44161 is a high-severity server-side request forgery vulnerability in fluentd, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Fluentd collects events from various data sources and writes them to files, RDBMS, NoSQL, IaaS, SaaS, Hadoop and so on. Prior to 1.19.3, the Fluentd out_http output plugin allows placeholders such as ${tag} in the endpoint configuration parameter, and if a placeholder value is derived from untrusted input an attacker can control the destination hostname of outbound HTTP requests and force requests to arbitrary internal services. This issue is fixed in version 1.19.3.
Weakness: CWE-918
Which versions are affected by CVE-2026-44161?
3 open source packages ship an affected version, including fluentd. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
fluentd Bitnami | All versions | 1.19.3 |
fluentd RubyGems | All versions | 1.19.3 |
fluentd RubyGems | All versions | 1.19.3 |
Products include Fluentd Fluentd.
How do I fix CVE-2026-44161?
Upgrade fluentd to 1.19.3 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-44161 being exploited?
There is no known exploitation of CVE-2026-44161 in the wild and no public exploit code.
Other vulnerabilities in fluentd
- CVE-2026-44024 Fluentd: Remote Code Execution (RCE) via Arbitrary File Write in `${tag}` Placeholder
- CVE-2017-10906 Fluentd Escape Sequence Injection Vulnerability
- CVE-2020-21514 Fluent Fluentd and Fluent-ui use default password
- CVE-2026-44025 Fluentd: Exposure of Sensitive Information via Monitor Agent API
- CVE-2026-44160 Fluentd: Denial of Service (DoS) via Gzip Decompression Bomb in `in_http` and `in_forward`
Sources
Also known as BIT-fluentd-2026-44161, CLEANSTART-2026-NY70538, CLEANSTART-2026-RY78730, GHSA-72f5-rr8c-r6gr, MINI-5h49-72r6-4m6x, MINI-6r37-5x78-v6m4 and 13 more.