Vulnerability
curl/libcurl: FTP path trickery leads to NIL byte out of bounds write
curl can be fooled into writing a zero byte out of bounds. This bug can trigger when curl is told to work on an FTP URL, with the setting to only issue a single CWD command (`--ftp-method singlecwd` or the libcurl alternative `CURLOPT_FTP_FILEMETHOD`). curl then URL-decodes the given path, calls strlen() on the result and deducts the length of the filename part to find the end of the directory within the buffer. It then writes a zero byte on that index, in a buffer allocated on the heap. If the directory part of the URL contains a "%00" sequence, the directory length might end up shorter than the filename path, making the calculation `size_t index = directory_len - filepart_len` end up with a huge index variable for where the zero byte gets stored: `heap_buffer[index] = 0`. On several architectures that huge index wraps and works as a negative value, thus overwriting memory *before* the intended heap buffer. By using different file part lengths and putting %00 in different places in the URL, an attacker that can control what paths a curl-using application uses can write that zero byte on different indexes.
No CVSS 3.x base score yet. Since April 2026 NVD only enriches priority CVEs (KEV, federal and critical software), so most CVEs are scored only if the assigning CNA included a score in the CVE record, or by GHSA for open-source packages. Last record update .
For interim severity, fall back on KEV / EXPLOIT signals and the EPSS percentile (lower panel). Re-check this CVE after one cron tick — the score lands automatically when the source publishes.
Above the FIRST 'patch on a priority schedule' threshold.
No VEX statements published for CVE-2018-1000120. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.
No exploitation, limited impact or prevalence