MEDIUM
CVE-2021-29433
CWE-20Published: April 15, 2021· Updated: Jun 17, 2026
4.3
CVSS v3.1
Official Description
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.
Technical Analysis
CVE-2021-29433 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
CVSS v3.1 Vector Breakdown
Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityLow
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Affected Vendors & Products
matrix1 product(s)
sydent
Source: NVD CPE · 1 total CPE entries
Exploit & PoC Resources
NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
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Official Patches & Advisories
All References (4)
→
https://github.com/matrix-org/sydent/commit/3175fd358ebc2c310eab7a3dbf296ce2bd54c1daPatch · Third Party Advisory
→
https://github.com/matrix-org/sydent/security/advisories/GHSA-pw4v-gr34-2553Patch · Third Party Advisory
→
https://github.com/matrix-org/sydent/commit/3175fd358ebc2c310eab7a3dbf296ce2bd54c1daPatch · Third Party Advisory
→
https://github.com/matrix-org/sydent/security/advisories/GHSA-pw4v-gr34-2553Patch · Third Party Advisory
Quick Facts
CVE IDCVE-2021-29433
CVSS Score4.3 / 10
SeverityMEDIUM
WeaknessCWE-20
CISA KEVNo
Affected1 vendor(s)
PublishedApr 15, 2021
Related CVEs (CWE-20)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-29433 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.