CVE-2021-29433
Denial of service (via resource exhaustion) due to improper input validation
Sydent is a reference Matrix identity server. In Sydent versions 2.2.0 and prior, sissing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion. A patch for the vulnerability is in version 2.3.0. No workarounds are known to exist.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
Denial of service (via resource exhaustion) due to improper input validation
Sydent is a reference Matrix identity server. In Sydent versions 2.2.0 and prior, sissing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion. A patch for the vulnerability is in version 2.3.0. No workarounds are known to exist.
- Record
CVE-2021-29433- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-20
- Updated
- 2026-11-02
EUVDEUVD-2021-0122
Sydent is a reference Matrix identity server. In Sydent versions 2.2.0 and prior, sissing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion. A patch for the vulnerability is in version 2.3.0. No workarounds are known to exist.
- Record
EUVD-2021-0122- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-pw4v-gr34-2553
Sydent DoS (via resource exhaustion) due to improper input validation
Impact
Missing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion.
Patches
Fixed by 3175fd3.
For more information
If you have any questions or comments about this advisory, email us at [email protected].
- Record
GHSA-pw4v-gr34-2553- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N - CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-20, CWE-400
- Updated
- 2026-11-02
NVD
Sydent is a reference Matrix identity server. In Sydent versions 2.2.0 and prior, sissing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion. A patch for the vulnerability is in version 2.3.0. No workarounds are known to exist.
- Record
CVE-2021-29433- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L - CVSS 2.0
- 4.0 Medium
AV:N/AC:L/Au:S/C:N/I:N/A:P - Weakness
- CWE-20, CWE-400
- Updated
- 2026-11-02
OSV
Sydent is a reference Matrix identity server. In Sydent versions 2.2.0 and prior, sissing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion. A patch for the vulnerability is in version 2.3.0. No workarounds are known to exist.
- Record
CVE-2021-29433- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L - Updated
- 2026-11-02
OSVGHSA-pw4v-gr34-2553
Sydent DoS (via resource exhaustion) due to improper input validation
Impact
Missing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion.
Patches
Fixed by 3175fd3.
For more information
If you have any questions or comments about this advisory, email us at [email protected].
- Record
GHSA-pw4v-gr34-2553- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N - CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-20, CWE-400
- Updated
- 2026-11-02
OSVPYSEC-2021-24 No score
Impact Missing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion. ### Patches Fixed by 3175fd3. ### Workarounds There are no known workarounds. ### References n/a ### For more information If you have any questions or comments about this advisory, email us at [email protected].
- Record
PYSEC-2021-24- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
matrix-sydentPyPI |
before 2.3.0 | 2.3.0 |
matrix-sydentPyPI |
before 2.3.0, plus listed versions 2.0.02.0.12.1.02.2.0 |
2.3.0 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-29433 is a medium vulnerability (CVSS 4.3) in Matrix Sydent, published April 15, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.93%, the 60th percentile. Fixed in matrix-sydent 2.3.0.
References
github.com/matrix-org/sydent/security/advisories/GHSA-pw4v-gr34-2553
nvd.nist.gov/vuln/detail/CVE-2021-29433
pypi.org/project/matrix-sydent