HOMEVULNERABILITIESCVE-2021-29431
MEDIUM

CVE-2021-29431

CWE-20Published: April 15, 2021· Updated: Jun 17, 2026

6.5
CVSS v3.1

Official Description

Sydent is a reference Matrix identity server. Sydent can be induced to send HTTP GET requests to internal systems, due to lack of parameter validation or IP address blacklisting. It is not possible to exfiltrate data or control request headers, but it might be possible to use the attack to perform an internal port enumeration. This issue has been addressed in in 9e57334, 8936925, 3d531ed, 0f00412. A potential workaround would be to use a firewall to ensure that Sydent cannot reach internal HTTP resources.

NVD Source

Technical Analysis

CVE-2021-29431 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.

A successful exploit results in complete confidentiality breach (data exposure), with a CVSS base score of 6.5.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityNone
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

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
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://github.com/matrix-org/sydent/commit/0f00412017f25619bc36c264b29ea96808bf310a
PATCHhttps://github.com/matrix-org/sydent/commit/3d531ed50d2fd41ac387f36d44d3fb2c62dd22d3
PATCHhttps://github.com/matrix-org/sydent/commit/8936925f561b0c352c2fa922d5097d7245aad00a
PATCHhttps://github.com/matrix-org/sydent/commit/9e573348d81df8191bbe8c266c01999c9d57cd5f
PATCHhttps://github.com/matrix-org/sydent/security/advisories/GHSA-9jhm-8m8c-c3f4
PATCHhttps://github.com/matrix-org/sydent/commit/0f00412017f25619bc36c264b29ea96808bf310a
PATCHhttps://github.com/matrix-org/sydent/commit/3d531ed50d2fd41ac387f36d44d3fb2c62dd22d3
PATCHhttps://github.com/matrix-org/sydent/commit/8936925f561b0c352c2fa922d5097d7245aad00a
PATCHhttps://github.com/matrix-org/sydent/commit/9e573348d81df8191bbe8c266c01999c9d57cd5f
PATCHhttps://github.com/matrix-org/sydent/security/advisories/GHSA-9jhm-8m8c-c3f4
ADVISORYhttps://github.com/matrix-org/sydent/releases/tag/v2.3.0
ADVISORYhttps://pypi.org/project/matrix-sydent/
ADVISORYhttps://github.com/matrix-org/sydent/releases/tag/v2.3.0
ADVISORYhttps://pypi.org/project/matrix-sydent/

All References (14)

→
https://github.com/matrix-org/sydent/commit/0f00412017f25619bc36c264b29ea96808bf310aPatch · Third Party Advisory
→
https://github.com/matrix-org/sydent/commit/3d531ed50d2fd41ac387f36d44d3fb2c62dd22d3Patch · Third Party Advisory
→
https://github.com/matrix-org/sydent/commit/8936925f561b0c352c2fa922d5097d7245aad00aPatch · Third Party Advisory
→
https://github.com/matrix-org/sydent/commit/9e573348d81df8191bbe8c266c01999c9d57cd5fPatch · Third Party Advisory
→
https://github.com/matrix-org/sydent/releases/tag/v2.3.0Release Notes · Third Party Advisory
→
https://github.com/matrix-org/sydent/security/advisories/GHSA-9jhm-8m8c-c3f4Patch · Third Party Advisory
→
https://pypi.org/project/matrix-sydent/Product · Third Party Advisory
→
https://github.com/matrix-org/sydent/commit/0f00412017f25619bc36c264b29ea96808bf310aPatch · Third Party Advisory
→
https://github.com/matrix-org/sydent/commit/3d531ed50d2fd41ac387f36d44d3fb2c62dd22d3Patch · Third Party Advisory
→
https://github.com/matrix-org/sydent/commit/8936925f561b0c352c2fa922d5097d7245aad00aPatch · Third Party Advisory
→
https://github.com/matrix-org/sydent/commit/9e573348d81df8191bbe8c266c01999c9d57cd5fPatch · Third Party Advisory
→
https://github.com/matrix-org/sydent/releases/tag/v2.3.0Release Notes · Third Party Advisory
→
https://github.com/matrix-org/sydent/security/advisories/GHSA-9jhm-8m8c-c3f4Patch · Third Party Advisory
→
https://pypi.org/project/matrix-sydent/Product · Third Party Advisory

Quick Facts

CVE IDCVE-2021-29431
CVSS Score6.5 / 10
SeverityMEDIUM
WeaknessCWE-20
CISA KEVNo
Affected1 vendor(s)
PublishedApr 15, 2021

Related CVEs (CWE-20)

CVE-2008-6826
10.0
CVE-2008-1331
10.0
CVE-2023-41917
10.0
CVE-2007-6494
10.0
CVE-2024-22476
10.0
CVE-2003-1425
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-29431 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.
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