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CVE-2010-3842

local file overwrite

Project curl Security Advisory, October 13th 2010 Permalink

VULNERABILITY

curl offers a command line option --remote-header-name (also usable as -J) which uses the filename of the Content-disposition: header when it saves the downloaded data locally.

curl attempts to cut off the directory parts from any given filename in the header to only store files in the current directory. It might overwrite a local file using the same name as the header specifies.

The stripping of the directory did not take backslashes into account. On some operating systems, backslashes are used to separate directories and filenames. This allows a rogue server to send back a response that overwrites a filename in the local machine that the user is allowed to write, potentially a system file, a command or a known executable.

Operating systems affected include Windows, Netware, MSDOS, OS/2 and Symbian.

This error is only present in the curl command line tool, it is NOT a problem of the library libcurl.

INFO

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2010-3842 to this issue.

CWE-30: Path Traversal

Severity: High

AFFECTED VERSIONS

Also note that curl is used by many applications, and not always advertised as such.

SOLUTION

libcurl 7.21.2 makes sure that it also strips off paths specified using backslashes as path separator.

RECOMMENDATIONS

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

A - Upgrade to curl and libcurl 7.21.2

B - Apply patch and rebuild

C - Stop using the --remote-header-name/-J option

TIMELINE

Dan Fandrich realized the problem exists and reported to the rest of the team on September 3 2010.

We discussed solutions and a first patch was written and tested on September 4th.

curl 7.21.2 was released on October 13th 2010, just before this flaw was publicly disclosed.

CREDITS

Thanks a lot!