Vulnerability · Published Sep 5, 2021 · Assigned by mitre
CVE-2021-40524
High 7.5
In plain English
A high-severity security flaw in the pure-ftpd package (Debian). There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 4.3% (higher than 91% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei. Fixed versions are available - upgrade the affected package.
Severity (CVSS NVD)7.5High
Exploit odds (30 days)4.3%top 8.8% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack tooling1Nuclei
Official description
In Pure-FTPd before 1.0.50, an incorrect max_filesize quota mechanism in the server allows attackers to upload files of unbounded size, which may lead to denial of service or a server hang. This occurs because a certain greater-than-zero test does not anticipate an initial -1 value. (Versions 1.0.23 through 1.0.49 are affected.)
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | pure-ftpd | 1.0.50-1 | DEBIAN-CVE-2021-40524 |
| Debian:13 | pure-ftpd | 1.0.50-1 | DEBIAN-CVE-2021-40524 |
| Ubuntu:22.04:LTS | pure-ftpd | no fix listed | UBUNTU-CVE-2021-40524 |
| Ubuntu:24.04:LTS | pure-ftpd | no fix listed | UBUNTU-CVE-2021-40524 |
| Ubuntu:25.10 | pure-ftpd | no fix listed | UBUNTU-CVE-2021-40524 |
| Ubuntu:26.04:LTS | pure-ftpd | no fix listed | UBUNTU-CVE-2021-40524 |
Affected products (as reported)
References
- https://github.com/jedisct1/pure-ftpd/pull/158 x_refsource_MISC
- https://github.com/jedisct1/pure-ftpd/compare/1.0.49...1.0.50 x_refsource_CONFIRM
- https://github.com/jedisct1/pure-ftpd/commit/37ad222868e52271905b94afea4fc780d83294b4 x_refsource_CONFIRM
- https://lists.debian.org/debian-lts-announce/2025/11/msg00003.html