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curl / Docs / Security Problems / GSS delegation too eager connection re-use

CVE-2023-27536: GSS delegation too eager connection re-use

Project curl Security Advisory, March 20th 2023 - Permalink


libcurl would reuse a previously created connection even when the GSS delegation (CURLOPT_GSSAPI_DELEGATION) option had been changed that could have changed the user's permissions in a second transfer.

libcurl keeps previously used connections in a connection pool for subsequent transfers to reuse if one of them matches the setup. However, this GSS delegation setting was left out from the configuration match checks, making them match too easily, affecting krb5/kerberos/negotiate/GSSAPI transfers.

We are not aware of any exploit of this flaw.


CVE-2023-27536 was introduced in commit ebf42c4be76df4, shipped in curl 7.22.0.

CWE-305: Authentication Bypass by Primary Weakness

Severity: Low


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


A fix for CVE-2023-27536


A - Upgrade curl to version 8.0.0

B - Apply the patch to your local version

C - Do not use the CURLOPT_GSSAPI_DELEGATION option


This issue was reported to the curl project on March 7, 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.


Thanks a lot!