CVE-2021-29431

HIGHNVD 7.77.7—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.7 under NVD CVSS v3. EPSS exploit probability: 1.2%, top 35% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this week
7.7
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.7Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
7.7
EG Score
7.7(medium)
EG Risk
40(Track)
EG Risk 40/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity77% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
64.8%
KEV
Not listed

Published

April 15, 2021

Last Modified

November 21, 2024

References (14)

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
matrix-sydent2.0.0, 2.0.1, 2.1.0, 2.2.02.3.0—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 14× in last 7d / 50× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-23 01:59 UTCEG score recompute
  2. 2026-07-22 22:46 UTCEG score recompute
  3. 2026-07-22 14:06 UTCEPSS rescore
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  42. 2026-06-13 08:43 UTCOSV refresh
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Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-29431?
CVE-2021-29431 is a high vulnerability published on April 15, 2021. 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…
When was CVE-2021-29431 disclosed?
CVE-2021-29431 was first published in the National Vulnerability Database on April 15, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-29431 actively exploited?
CVE-2021-29431 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 64.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-29431?
CVE-2021-29431 has a CVSS v3 base score of 7.7 (NVD).
How do I remediate CVE-2021-29431?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-29431, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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