Fluentd CVE-2026-44160
HIGH
GHSA-j9cw-hwqf-85w7
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Unauthenticated network requests to in_http/in_forward (PR:N, AV:N, AC:L) with no UI; impact is availability-only (A:H, C:N/I:N) via OOM, no scope change.
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:U/C:N/I:N/A:H
Lifecycle Timeline
2DescriptionCVE.org
Fluentd's in_http and in_forward plugins support receiving gzip-compressed data. While Fluentd correctly enforces size limits on the incoming compressed payloads (e.g., via body_size_limit or chunk_size_limit), it was discovered that there is no limit enforced on the size of the decompressed data.
If a Fluentd instance is exposed to untrusted networks, an attacker can send a maliciously crafted, highly compressed payload. When Fluentd attempts to decompress this payload in memory, it will expand to an excessive size, completely bypassing the intended payload size limits.
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
v1.19.3
Workarounds
If an immediate upgrade is not possible, users are strongly advised to apply the following mitigations:
- Restrict Network Access
- Ensure that Fluentd input ports (such as
9880forin_httpand24224forin_forward) 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 developers 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.
AnalysisAI
Denial of service in Fluentd (rubygems package, versions <= 1.19.2) lets remote attackers crash the log collector by sending a gzip decompression bomb to the in_http (default port 9880) or in_forward (default port 24224) plugins. Although Fluentd enforces body_size_limit and chunk_size_limit on the compressed payload, it applies no ceiling on the decompressed output, so a tiny crafted payload expands in memory until the OS OOM-kills the process. …
Unlock full vulnerability intelligence
- Risk assessment & exploitation conditions
- Attack chain visualization
- Remediation with exact patch versions
- Threat intelligence from 22 sources
- Personal watchlist & email alerts
Free forever · No credit card required
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that a vulnerable Fluentd instance (<= 1.19.2) have an in_http or in_forward listener reachable by the attacker AND that the input accept gzip-compressed data - both plugins support gzip ingestion that triggers the unbounded in-memory inflation. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (7.5 High) is internally consistent: network-reachable, low complexity, no privileges or interaction, with impact confined to availability (C:N/I:N) - appropriate for a pure DoS. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who can reach an internet- or tenant-exposed Fluentd in_http (9880) or in_forward (24224) port crafts a small, extremely high-ratio gzip payload (a decompression bomb) and POSTs or forwards it. Fluentd accepts it because the compressed size is under the configured limit, then inflates it in memory until consumption spikes and the kernel OOM-kills the process, halting all log collection and forwarding on that node. … |
| Remediation | Vendor-released patch: upgrade to Fluentd 1.19.3, which enforces size limits on decompressed payloads (PR #5393); see https://github.com/fluent/fluentd/releases/tag/v1.19.3 and advisory GHSA-j9cw-hwqf-85w7. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Identify all Fluentd instances running version 1.19.2 or earlier and determine network exposure of ports 9880 (in_http) and 24224 (in_forward). …
Sign in for detailed remediation steps and compensating controls.
Threat intelligence, references, and detailed analysis are available after sign-in.
The ngx_http_parse_chunked function in http/ngx_http_parse.c in nginx 1.3.9 through 1.4.0 allows remote attackers to cau
A critical vulnerability in Kubernetes ingress-nginx controller allows unauthenticated attackers with pod network access
nginx 0.8.41 through 1.4.3 and 1.5.x before 1.5.7 allows remote attackers to bypass intended restrictions via an unescap
An issue was discovered on GL.iNet devices before version 4.5.0. Rated critical severity (CVSS 9.8), this vulnerability
Nginx versions since 0.5.6 up to and including 1.13.2 are vulnerable to integer overflow vulnerability in nginx range fi
The resolver in nginx before 1.8.1 and 1.9.x before 1.9.10 allows remote attackers to cause a denial of service (invalid
Kubernetes ingress-nginx contains a configuration injection vulnerability via the mirror-target and mirror-host Ingress
A security issue was discovered in ingress-nginx https://github.com/kubernetes/ingress-nginx where the `auth-url` Ingres
A security issue was discovered in ingress-nginx https://github.com/kubernetes/ingress-nginx where the `auth-tls-match-c
Roxy-WI is a web interface for managing Haproxy, Nginx, Apache and Keepalived servers. Rated critical severity (CVSS 9.8
The STARTTLS implementation in mail/ngx_mail_smtp_handler.c in the SMTP proxy in nginx 1.5.x and 1.6.x before 1.6.1 and
Heap buffer overflow in NGINX Plus and NGINX Open Source ngx_http_rewrite_module allows remote attackers to crash worker
Same technique Denial Of Service
View allShare
External POC / Exploit Code
Leaving vuln.today