CVE-2021-40524
In Pure-FTPd 1.0.49, an incorrect max_filesize quota mechanism in the server allows attackers to...
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.)
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
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.)
- Record
CVE-2021-40524- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 5.0 Medium
AV:N/AC:L/Au:N/C:N/I:N/A:P - Weakness
- CWE-434
- Updated
- 2026-11-02
CVE List No score
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.)
- Record
CVE-2021-40524- Updated
- 2026-11-02
EUVDEUVD-2021-27700 No score
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.)
- Record
EUVD-2021-27700- Updated
- 2026-11-02
GitHub AdvisoriesGHSA-p53v-96v3-p5jg
In Pure-FTPd 1.0.49, an incorrect max_filesize quota mechanism in the server allows attackers to...
In Pure-FTPd 1.0.49, 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.
- Record
GHSA-p53v-96v3-p5jg- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-434
- Updated
- 2026-11-02
OSV
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.)
- Record
CVE-2021-40524- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVDEBIAN-CVE-2021-40524
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.)
- Record
DEBIAN-CVE-2021-40524- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVUBUNTU-CVE-2021-40524
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.)
- Record
UBUNTU-CVE-2021-40524- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVopenSUSE-SU-2024:11773-1 No score
pure-ftpd-1.0.50-1.1 on GA media
These are all security issues fixed in the pure-ftpd-1.0.50-1.1 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2024:11773-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
pure-ftpdDebian:12 |
before 1.0.50-1 | 1.0.50-1 |
pure-ftpdDebian:13 |
before 1.0.50-1 | 1.0.50-1 |
pure-ftpdDebian:11 |
before 1.0.49-4.1+deb11u1, plus listed versions 1.0.49-4.1 |
1.0.49-4.1+deb11u1 |
pure-ftpdUbuntu:16.04:LTS |
All versions, plus listed versions 1.0.36-3.21.0.36-3.2build11.0.36-3.2+deb8u1build0.16.04.1 |
None known |
pure-ftpdUbuntu:18.04:LTS |
All versions, plus listed versions 1.0.46-11.0.46-1build11.0.46-1ubuntu18.04.1 |
None known |
pure-ftpdUbuntu:20.04:LTS |
All versions, plus listed versions 1.0.47-3build11.0.49-11.0.49-21.0.49-31.0.49-41.0.49-4ubuntu0.1 |
None known |
pure-ftpdUbuntu:22.04:LTS |
All versions, plus listed versions 1.0.49-4.1build11.0.50-21.0.50-2.11.0.50-2.1ubuntu0.22.04.1 |
None known |
pure-ftpdUbuntu:24.04:LTS |
All versions, plus listed versions 1.0.50-2.1build11.0.50-2.1ubuntu11.0.50-2.21.0.50-2.2build11.0.50-2.2build2 |
None known |
pure-ftpdUbuntu:25.10 |
All versions, plus listed versions 1.0.50-2.2build3 |
None known |
pure-ftpdUbuntu:26.04:LTS |
All versions, plus listed versions 1.0.50-2.2build31.0.50-2.2build4 |
None known |
pure-ftpdopenSUSE:Tumbleweed From an advisory covering 4 CVEs |
before 1.0.50-1.1 | 1.0.50-1.1 |
Public exploits
Links only. Every CVE stores no exploit code.
| Source | Link | Date |
|---|---|---|
| Nuclei | Pure-FTPd 1.0.23 < 1.0.50 - Arbitrary File Upload |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| first indexed | CVE List, EUVD, GitHub Advisories, Nuclei, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-40524 is a high vulnerability (CVSS 7.5) in Pureftpd Pure-ftpd, published September 5, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 4.29%, the 91st percentile. Fixed in pure-ftpd 1.0.50-1.
References
github.com/jedisct1/pure-ftpd/pull/158
lists.debian.org/debian-lts-announce/2025/11/msg00003.html
nvd.nist.gov/vuln/detail/CVE-2021-40524