CVE-2021-33900

StartTLS and SASL confidentiality protection bypass

7.5 HighFix available

While investigating DIRSTUDIO-1219 it was noticed that configured StartTLS encryption was not applied when any SASL authentication mechanism (DIGEST-MD5, GSSAPI) was used. While investigating DIRSTUDIO-1220 it was noticed that any configured SASL confidentiality layer was not applied. This issue affects Apache Directory Studio version 2.0.0.v20210213-M16 and prior versions.

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: High
Integrity: None
Availability: None

Exploit likelihood

0.79%Up 0.4 points since Jul 26, 2021

What each source reports

NVD Score used 7.5

Record: CVE-2021-33900
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS 2.0: 5.0 MediumAV:N/AC:L/Au:N/C:P/I:N/A:N
Weakness: CWE-311, CWE-319
Updated: 2026-11-02

CVE List No score

StartTLS and SASL confidentiality protection bypass

Record: CVE-2021-33900
Weakness: CWE-311
Updated: 2026-11-02

EUVDEUVD-2021-1565 No score

Record: EUVD-2021-1565
Updated: 2026-11-03

GitHub AdvisoriesGHSA-4x25-f45x-grv5 7.5

Missing encryption in Apache Directory Studio

Record: GHSA-4x25-f45x-grv5
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness: CWE-311, CWE-319
Updated: 2026-11-02

OSV 7.5

Record: CVE-2021-33900
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Updated: 2026-11-02

OSVGHSA-4x25-f45x-grv5 7.5

Missing encryption in Apache Directory Studio

Record: GHSA-4x25-f45x-grv5
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness: CWE-311, CWE-319
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-33900 7.5

Record: UBUNTU-CVE-2021-33900
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`org.apache.directory.studio:org.apache.directory.studio.parent` Maven	through 2.0.0.v20210213-M16	2.0.0.v20210717-M17
`org.apache.directory.studio:org.apache.directory.studio.parent` Maven	before 2.0.0.v20210717-M17, plus listed versions 2.0.0.v20150606-M92.0.0.v20151221-M102.0.0.v20161101-M122.0.0.v20170904-M132.0.0.v20180908-M142.0.0.v20200411-M152.0.0.v20210213-M16	2.0.0.v20210717-M17
`apache-directory-server` Ubuntu:16.04:LTS	All versions, plus listed versions 2.0.0~M15-12.0.0~M15-22.0.0~M15-3	None known
`apache-directory-server` Ubuntu:18.04:LTS	All versions, plus listed versions 2.0.0~M15-42.0.0~M24-2~18.04	None known
`apache-directory-server` Ubuntu:20.04:LTS	All versions, plus listed versions 2.0.0~M24-3	None known
`apache-directory-server` Ubuntu:22.04:LTS	All versions, plus listed versions 2.0.0~M24-4	None known
`apache-directory-server` Ubuntu:24.04:LTS	All versions, plus listed versions 2.0.0~M26-12.0.0~M26-32.0.0~M26-4	None known
`apache-directory-server` Ubuntu:25.10	All versions, plus listed versions 2.0.0~M26-5	None known
`apache-directory-server` Ubuntu:26.10	All versions, plus listed versions 2.0.0~M26-5build12.0.0~M26-62.0.0~M26-7	None known
`apache-directory-server` Ubuntu:26.04:LTS	All versions, plus listed versions 2.0.0~M26-52.0.0~M26-5build1	None known

History

History
Recorded	Changed	Sources
Nov 3, 2026	aliases	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-33900 is a high vulnerability (CVSS 7.5) in Apache Directory Studio, published July 26, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.79%, the 56th percentile. Fixed in org.apache.directory.studio:org.apache.directory.studio.parent 2.0.0.v20210717-M17.