Fluentd is Vulnerable to Denial of Service (DoS) via Gzip Decompression Bomb in in_http and in_forward

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-44160: 0.62% estimated exploitation activity in the next 30 days; percentile 49.75 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Fluentd's inhttp and inforward plugins support receiving gzip-compressed data. While Fluentd correctly enforces size limits on the incoming compressed payloads (e.g., via bodysizelimit or chunksizelimit), 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…

Published by the source

26 Jun 2026, 16:35 UTC

Last modified by the source

26 Jun 2026, 16:35 UTC

Source last checked

26 Oct 2026, 15:52 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-j9cw-hwqf-85w7

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# Patch Next advisory brief: CVE-2026-44160

Advisory: Fluentd is Vulnerable to Denial of Service (DoS) via Gzip Decompression Bomb in `in_http` and `in_forward`
IDs: CVE-2026-44160, GHSA-j9cw-hwqf-85w7
Record: https://patchnext.com/advisories/cve-2026-44160 (revision 1, source checked 26 Oct 2026, 15:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: fluentd 1.19.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems fluentd: affected <= 1.19.2; fixed in 1.19.3

## Suggested inspection (read-only)
- RubyGems fluentd: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on fluentd.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-j9cw-hwqf-85w7 (GitHub-reviewed advisory GHSA-j9cw-hwqf-85w7 lists affected ranges: RubyGems fluentd >=0 <=1.19.2)

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