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Fencer Vulns
high 7.5

CVE-2021-40524 json

In Pure-FTPd before 1.0.50, an incorrect max_filesize quota mechanism in the server allows attackers to upload files of unbounded size, whi…

published 2021-09-05 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-27700

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
4.3%
EPSS 4.3% chance of exploitation in 30 days, percentile 91%
public exploits
0
none known, plus a Nuclei check

Summary

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.)

Patch / fix

  • pureftpd pure-ftpd 1.0.50
  • pure-ftpd Debian 13, Debian 12 1.0.50-1

debian advisories DEBIAN-CVE-2021-40524

  • pure-ftpd openSUSE Tumbleweed 1.0.50-1.1

opensuse advisories openSUSE-SU-2024:11773-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-40524 updated cvss 7.5

pure-ftpd: unbounded file size in file upload

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

4.29% chance of exploitation in the next 30 days, higher than 91% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • Nuclei template Pure-FTPd 1.0.23 < 1.0.50 - Arbitrary File Upload nuclei detection template
  • github.com https://github.com/jedisct1/pure-ftpd/pull/158 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Classification

Weakness
  • CWE-434 Unrestricted Upload of File with Dangerous Type

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.