libcurl-using applications can ask for a specific client certificate to be used in a transfer.

Summary

libcurl-using applications can ask for a specific client certificate to be used in a transfer. This is done with the `CURLOPT_SSLCERT` option (`--cert` with the command line tool).When libcurl is built to use the macOS native TLS library Secure Transport, an application can ask for the client certificate by name or with a file name - using the same option. If the name exists as a file, it will be used instead of by name.If the appliction runs with a current working directory that is writable by other users (like `/tmp`), a malicious user can create a file name with the same name as the app wants to use by name, and thereby trick the application to use the file based cert instead of the one referred to by name making libcurl send the wrong client certificate in the TLS connection handshake.

Timeline

1. Aug 5, 2021, 12:00 AM UTCCVE published
2. May 28, 2026, 7:49 PM UTCCISA SSVC assessment

   Exploitation: poc · Automatable: yes · Technical impact: partial

3. Oct 14, 2026, 11:13 AM UTCRecord last updated
4. Oct 22, 2026EPSS reached 10%

   FIRST estimates at least a 10% chance of exploitation in the next 30 days

Affected versions

• n/a https://github.com/curl/curl

  curll 7.33.0 to and include 7.77.0

References 11