Vulnerability
curl/libcurl: SMTP send heap buffer overflow
curl might overflow a heap based memory buffer when sending data over SMTP and using a reduced read buffer. When sending data over SMTP, curl allocates a separate "scratch area" on the heap to be able to escape the uploaded data properly if the uploaded data contains data that requires it. The size of this temporary scratch area was mistakenly made to be `2 * sizeof(download_buffer)` when it should have been made `2 * sizeof(upload_buffer)`. The upload and the download buffer sizes are identically sized by default (16KB) but since version 7.54.1, curl can resize the download buffer into a smaller buffer (as well as larger). If the download buffer size is set to a value smaller than 10923, the `Curl_smtp_escape_eob()` function might overflow the scratch buffer when sending contents of sufficient size and contents. The curl command line tool lowers the buffer size when `--limit-rate` is set to a value smaller than 16KB.
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.
Mid-pack — moderate exploitation likelihood.
No VEX statements published for CVE-2018-0500. 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