curl overwrite local file with -J
curl can be tricked by a malicious server to overwrite a local file when using `-J` (`--remote-header-name`) and `-i` (`--include`) in the same command line. The command line tool offers the `-J` option that saves a remote file using the filename present in the `Content-Disposition:` response header. curl then refuses to overwrite an existing local file using the same name, if one already exists in the current directory. The `-J` flag is designed to save a response body, and so it does not work together with `-i` and there is logic that forbids it. However, the check is flawed and does not properly check for when the options are used in the reversed order: first using `-J` and then `-i` were mistakenly accepted. The result of this mistake was that incoming HTTP headers could overwrite a local file if one existed, as the check to avoid the local file was done first when body data was received, and due to the mistake mentioned above, it could already have received and saved headers by that time. The saved file would only get response headers added to it, as it would abort the saving when the first body byte arrives. A malicious server could however still be made to send back virtually anything as headers and curl would save them like this, until the first CRLF-CRLF sequence appears. (Also note that `-J` needs to be used in combination with `-O` to have any effect.)
02 / AFFECTED SOFTWARE
Affected packages
77 explicit affected versions
158 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
curl 7.20.0 through 7.70.0 is vulnerable to improper restriction of names for files and other resources that can lead too overwriting a local file when the -J flag is used.
curl can be tricked by a malicious server to overwrite a local file when using `-J` (`--remote-header-name`) and `-i` (`--include`) in the same command line. The command line tool offers the `-J` option that saves a remote file using the filename present in the `Content-Disposition:` response header. curl then refuses to overwrite an existing local file using the same name, if one already exists in the current directory. The `-J` flag is designed to save a response body, and so it does not work together with `-i` and there is logic that forbids it. However, the check is flawed and does not properly check for when the options are used in the reversed order: first using `-J` and then `-i` were mistakenly accepted. The result of this mistake was that incoming HTTP headers could overwrite a local file if one existed, as the check to avoid the local file was done first when body data was received, and due to the mistake mentioned above, it could already have received and saved headers by that time. The saved file would only get response headers added to it, as it would abort the saving when the first body byte arrives. A malicious server could however still be made to send back virtually anything as headers and curl would save them like this, until the first CRLF-CRLF sequence appears. (Also note that `-J` needs to be used in combination with `-O` to have any effect.)
05 / REFERENCES