Critical Use-After-Free Vulnerability in curl Package

curl Updated 02 Oct 2025

Summary

01/08/2018

Disclosed on

N/A

Severity

Yes i

Fix available

High

Severity

7.5

CVSS Score

ALPINE-CVE-2016-8623: A flaw was found in curl before version 7.51.0. Affects curl versions < 7.51.0-r0. Fixed in 7.51.0-r0. How to fix ↓

Free scan

Check if this vulnerability affects your application

Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.

Check my app free

No signup required · Results in about 60 seconds

Upload your dependency manifest or SBOM

Drag & drop your file here or Browse

Java Javascript PHP Python Go Rust Ruby Dart C/C++ Elixir CycloneDX SPDX

Upload a supported dependency manifest or SBOM. No installation or source-code access required.

See supported files and SBOM formats

SBOM sbom.json · bom.json · bom.xml · *.spdx.json · *.cdx.json · *.cdx.xml

Java pom.xml · gradle.lockfile · buildscript-gradle.lockfile

Javascript package-lock.json · yarn.lock · pnpm-lock.yaml

PHP composer.lock

Python poetry.lock · requirements.txt · Pipfile.lock

Go go.mod

Rust Cargo.lock

Ruby Gemfile.lock

Dart pubspec.lock

C/C++ conan.lock

Elixir mix.lock

Enter your work email to receive your report link.

Verify your email to view the full report and start 30 days of continuous monitoring. No credit card required.

Background

curl is a widely-used command-line tool and library for transferring data with URLs. It supports various protocols, including HTTP, HTTPS, FTP, and more. curl is essential for developers and system administrators for tasks such as downloading files, testing APIs, and automating web interactions. However, a critical vulnerability has been identified in curl versions prior to 7.51.0, which could lead to severe security risks.

Vulnerability Detail

A flaw was found in curl before version 7.51.0. The way curl handles cookies permits other threads to trigger a use-after-free condition, leading to potential information disclosure. This vulnerability can be exploited by attackers to access sensitive data, making it crucial for users to address it promptly. The CVSS score for this vulnerability is 7.5, indicating a high severity level.

How To Fix

Minimum fixed version

7.51.0-r0

This is the first release that contains the fix.

sudo apk add --upgrade curl

Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →

Workaround

As a temporary workaround, users can avoid using curl in scenarios where cookie handling is critical until they can update to a secure version. Additionally, consider using alternative tools for data transfer that do not exhibit this vulnerability.

Conclusion

The use-after-free vulnerability in curl poses significant risks, including potential information disclosure. Users are strongly encouraged to update to the patched version 7.51.0 or later to mitigate these risks. Utilizing tools like Vulert can help monitor for such vulnerabilities in real-time.

See every vulnerability recorded for curl →