CVE-2023-27535

FTP too eager connection reuse

Project curl Security Advisory, March 20th 2023 - Permalink

VULNERABILITY

libcurl would reuse a previously created FTP connection even when one or more options had been changed that could have made the effective user a very different one, thus leading to doing the second transfer with the wrong credentials.

libcurl keeps previously used connections in a connection pool for subsequent transfers to reuse if one of them matches the setup. However, several FTP settings were left out from the configuration match checks, making them match too easily. The settings in questions are CURLOPT_FTP_ACCOUNT, CURLOPT_FTP_ALTERNATIVE_TO_USER, CURLOPT_FTP_SSL_CCC and CURLOPT_USE_SSL level.

INFO

CWE-305: Authentication Bypass by Primary Weakness

Severity: Medium

AFFECTED VERSIONS

• Affected versions: curl 7.13.0 to and including 7.88.1
• Not affected versions: curl < 7.13.0 and curl >= 8.0.0
• Introduced-in: https://github.com/curl/curl/commit/177dbc7be07125582

libcurl is used by many applications, but not always advertised as such!

SOLUTION

• Fixed-in: https://github.com/curl/curl/commit/8f4608468b890dc

RECOMMENDATIONS

A - Upgrade curl to version 8.0.0

B - Apply the patch to your local version

TIMELINE

This issue was reported to the curl project on March 5, 2023. We contacted distros@openwall on March 13, 2023.

curl 8.0.0 was released on March 20 2023, coordinated with the publication of this advisory.

CREDITS

• Reported-by: Harry Sintonen
• Patched-by: Daniel Stenberg

Thanks a lot!