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fzf vulnerable to denial of service through quadratic HTTP request-body accumulationGHSA-mvmf-94v6-879g

Fix: junegunn/fzf@7963a2c

GHSA-mvmf-94v6-879g is a CWE-407 vulnerability in github.com/junegunn/fzf. A fix is available for github.com/junegunn/fzf — see the affected versions and patch details below.

Also known asCVE-2026-53433GO-2026-6620
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • 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 GHSA-mvmf-94v6-879g.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs31th percentile — riskier than 31% of all scored CVEsHighest risk
0.00%0.29%0.59%0.88%0.1%0.2%0.4%0.4%0.4%Jul 26Sep 26Oct 26

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

Real-World Exposure

1 pkg affected
🐹github.com/junegunn/fzf

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

Description

fzf is vulnerable to a Denial of Service (DoS) due to inefficient HTTP body processing in the --listen mode due to inefficient HTTP body processing using repeated string concatenation, resulting in quadratic time complexity (O(n²)). A crafted POST request with many small segments can trigger excessive CPU usage during request handling.This allows a single malicious request to monopolize the single‑threaded HTTP server, blocking all other clients and resulting in denial of service.

This issue was fixed in version 0.73.1.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/junegunn/fzfall versions0.73.1go get github.com/junegunn/fzf@v0.73.1

Affected Products

1 product · 1 configurations
Application
fzfjunegunn
< 0.73.1
range

Detection & mitigation playbook

Open-source dependency
  1. Detect

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

  2. Fix

    Update github.com/junegunn/fzf to 0.73.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mvmf-94v6-879g is resolved across your whole dependency graph.

  3. 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.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

A flaw was found in fzf, a command-line fuzzy finder. When fzf is running in --listen mode (a non-default, opt-in feature), inefficient HTTP body processing using repeated string concatenation results in quadratic time complexity. A crafted POST request can monopolize the single-threaded HTTP server, causing denial of…

Workaround published by Red Hat
Do not use fzf's --listen mode in untrusted network environments. If --listen is required, restrict network access to the fzf listener port using firewall rules.
Source: Red Hat security advisory for GHSA-mvmf-94v6-879g (CC BY 4.0)

Frequently Asked Questions

fzf is vulnerable to a Denial of Service (DoS) due to inefficient HTTP body processing in the --listen mode due to inefficient HTTP body processing using repeated string concatenation, resulting in quadratic time complexity (O(n²)). A crafted POST request with many small segments can trigger excessive CPU usage during request handling.This allows a single malicious request to monopolize the single‑threaded HTTP server, blocking all other clients and resulting in denial of service. This issue was fixed in version 0.73.1.
O3 Security · Impact-Aware SCA

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