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curl / Docs / curl CVEs / not verifying certs for TLS to IP address / Secure Transport


not verifying certs for TLS to IP address / Secure Transport

Project curl Security Advisory, March 26th 2014 Permalink


When asked to do a TLS connection (HTTPS, FTPS, IMAPS, etc) to a URL specified with an IP address instead of a name, libcurl would wrongly not verify the server's name in the certificate. The signature (whether it was signed by a trusted CA) and validity (whether the date was within the certificate's lifetime and it was not revoked) verification was still performed.

This is a problem in libcurl built to use the Secure Transport backend. Secure Transport is the TLS library present and used on Mac OS X and iOS.

Only users on Mac OS X or iOS can be affected by this. And only if libcurl was built to use the native TLS backend library.

This problem was initially used as an example of the Apple SSL bug that hit the news in late February 2014 but that was not correct.


The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2014-1263 to this issue.

CWE-297: Improper Validation of Certificate with Host Mismatch

Severity: Medium


This flaw has existed ever since libcurl started to support the Secure Transport backend.

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


libcurl 7.36.0 makes sure that all TLS using requests verify the host name even if specified as an IP address in the URL.


We suggest you take one of the following actions immediately, in order of preference:

A - Upgrade to curl and libcurl 7.36.0

B - Apply the patch and rebuild libcurl

C - Rebuild libcurl to use another TLS backend


It was discovered by the curl project during late February 2014.

libcurl 7.36.0 was released on March 26th 2014, coordinated with the publication of this advisory.


This was indirectly reported by numerous people and it was also clarified by Adam Langley that it wasn't the problem Apple themselves fixed. Roland Moriz is credited in Apple's security note.

Nick Zitzmann helped coordinate the bug fix.

Apple claims to have fixed this problem in an update of their own. That was done independently from and without informing the curl project.

Thanks a lot!