Critical Denial of Service Vulnerability in curl Package

curl Updated 02 Oct 2025

Summary

14/03/2018

Disclosed on

N/A

Severity

Yes i

Fix available

High

Severity

7.5

CVSS Score

ALPINE-CVE-2018-1000121: A NULL pointer dereference exists in curl 7.21.0 to and including curl 7.58.0 in the LDAP code that allows an attacker to cause a denial of service. Affects curl versions < 7.59.0-r0. Fixed in 7.59.0-r0. How to fix ↓

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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, certain versions of curl are vulnerable to a NULL pointer dereference in the LDAP code, which can lead to a denial of service.

Vulnerability Detail

A NULL pointer dereference exists in curl versions 7.21.0 to 7.58.0 specifically in the LDAP code. This vulnerability allows an attacker to exploit the flaw, potentially causing the application to crash and resulting in a denial of service. The vulnerability is critical, with a CVSS score of 7.5, indicating that it poses a significant risk to systems using affected versions of curl.

How To Fix

Minimum fixed version

7.59.0-r0

This is the first release that contains the fix.

sudo apk add --upgrade curl

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Workaround

As a temporary workaround, you can disable LDAP support in curl if it is not needed for your application. This can be done by configuring curl without LDAP support during installation or by using a different version of curl that does not include LDAP functionality.

Conclusion

The curl package has a critical vulnerability that can lead to denial of service due to a NULL pointer dereference in its LDAP code. Users are strongly advised to update to the patched version to mitigate this risk. For those unable to update immediately, disabling LDAP support can serve as a temporary measure.

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