EUVD-2026-40303
GHSA-mvmf-94v6-879g
Severity by source
CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Local attack vector because --listen binds locally; PR:L reflects access needed to reach the socket; pure availability impact with no C or I consequence.
Primary rating from Vendor (CERT-PL).
CVSS VectorVendor: CERT-PL
Lifecycle Timeline
2DescriptionCVE.org
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.
AnalysisAI
Denial of service in fzf's --listen mode HTTP server arises from quadratic-time (O(n²)) body processing caused by repeated string concatenation when reading POST request payloads. All fzf releases prior to 0.73.1 are affected when the --listen flag is explicitly activated to expose the embedded HTTP server. An attacker with access to the listening socket can send a single crafted POST request with many small body segments to monopolize the single-threaded server, blocking all other clients indefinitely. No public exploit identified at time of analysis; vendor-released patch is available in version 0.73.1.
Technical ContextAI
fzf is a general-purpose command-line fuzzy finder written in Go. Its --listen mode exposes a local HTTP server that accepts POST requests to drive fzf programmatically (e.g., for editor integrations). The root cause is CWE-407 (Algorithmic Complexity): the HTTP body is assembled by repeatedly concatenating small string segments rather than using an efficient buffered builder, producing O(n²) time complexity as input size grows. Because the embedded server is single-threaded, one long-running request blocks all concurrent handling. Affected products are identified by CPE cpe:2.3:a:fzf:fzf:*:*:*:*:*:*:*:*, covering all versions up to but not including 0.73.1. The fix is in commit 7963a2c6586c0b9eaa89b8995de8f0e08cf8a4ce on the junegunn/fzf repository.
RemediationAI
Upgrade fzf to version 0.73.1 or later, which contains the upstream fix (commit 7963a2c6586c0b9eaa89b8995de8f0e08cf8a4ce) replacing the inefficient string concatenation with a buffered approach. If immediate upgrade is not possible, the most effective compensating control is to avoid starting fzf with the --listen flag entirely, as the vulnerability only exists when this mode is active. If --listen mode is operationally required, restrict access to the listening socket via OS-level firewall rules or by ensuring the socket binds only to localhost and is not reachable from untrusted users on shared systems. Restricting access to the port used by --listen (verify the configured port in your environment) to only trusted local processes eliminates the network-reachable attack surface. Note that these workarounds do not address the underlying algorithmic flaw; upgrade to 0.73.1 as soon as feasible.
Same weakness CWE-407 – Inefficient Algorithmic Complexity
View allSame technique Denial Of Service
View allVendor StatusVendor
SUSE
Severity: ImportantShare
External POC / Exploit Code
Leaving vuln.today