libcurl may read outside of a heap allocated buffer when doing FTP. When libcurl connects to an FTP server and successfully logs in (anonymous or not), it asks the server for the current directory with the `PWD` command. The server then responds with a 257 response containing the path, inside double quotes. The returned path name is then kept by libcurl for subsequent uses. Due to a flaw in the string parser for this directory name, a directory name passed like this but without a closing double quote would lead to libcurl not adding a trailing NUL byte to the buffer holding the name. When libcurl would then later access the string, it could read beyond the allocated heap buffer and crash or wrongly access data beyond the buffer, thinking it was part of the path. A malicious server could abuse this fact and effectively prevent libcurl-based clients to work with it - the PWD command is always issued on new FTP connections and the mistake has a high chance of causing a segfault. The simple fact that this has issue remained undiscovered for this long could suggest that malformed PWD responses are rare in benign servers. We are not aware of any exploit of this flaw. This bug was introduced in commit [415d2e7cb7](https://github.com/curl/curl/commit/415d2e7cb7), March 2005. In libcurl version 7.56.0, the parser always zero terminates the string but also rejects it if not terminated properly with a final double quote.

Affected: Ubuntu:14.04:LTS: curl, Ubuntu:16.04:LTS: curl

Daniel Stenberg discovered that curl incorrectly handled large floating point output. A remote attacker could use this issue to cause curl to crash, resulting in a denial of service, or possibly execute arbitrary code. This issue only affected Ubuntu 14.04 LTS and Ubuntu 16.04 LTS. (CVE-2016-9586)

Even Rouault discovered that curl incorrectly handled large file names when doing TFTP transfers. A remote attacker could use this issue to cause curl to crash, resulting in a denial of service, or possibly obtain sensitive memory contents. (CVE-2017-1000100)

Brian Carpenter and Yongji Ouyang discovered that curl incorrectly handled numerical range globbing. A remote attacker could use this issue to cause curl to crash, resulting in a denial of service, or possibly obtain sensitive memory contents. (CVE-2017-1000101)

Max Dymond discovered that curl incorrectly handled FTP PWD responses. A remote attacker could use this issue to cause curl to crash, resulting in a denial of service. (CVE-2017-1000254)

Brian Carpenter discovered that curl incorrectly handled the --write-out command line option. A local attacker could possibly use this issue to obtain sensitive memory contents. (CVE-2017-7407)