CVE-2021-42564

MEDIUMNVD 5.45.4—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.4 under NVD CVSS v3. EPSS exploit probability: 0.7%, top 52% 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
5.4
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 1%CVSS: 5.4Exploit: NoneExposed: 0

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

An open redirect through HTML injection in confidential messages in Cryptshare before 5.1.0 allows remote attackers (with permission to provide confidential messages via Cryptshare) to redirect targeted victims to any URL via the '

CVSS v3
5.4
EG Score
5.4(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: 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
Severity54% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
48.0%
KEV
Not listed

Published

November 30, 2021

Last Modified

November 21, 2024

References (2)

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× 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.

Showing the most recent 100 of 106 total refreshes for this CVE.

  1. 2026-07-23 14:16 UTCEPSS rescore
  2. 2026-07-23 02:04 UTCEG score recompute
  3. 2026-07-22 22:51 UTCEG score recompute
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Frequently asked(5)

What is CVE-2021-42564?
CVE-2021-42564 is a medium vulnerability published on November 30, 2021. An open redirect through HTML injection in confidential messages in Cryptshare before 5.1.0 allows remote attackers (with permission to provide confidential messages via Cryptshare) to redirect targeted victims to any URL via the '<meta http-equiv="refresh"' substring in the editor parameter.
When was CVE-2021-42564 disclosed?
CVE-2021-42564 was first published in the National Vulnerability Database on November 30, 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-2021-42564 actively exploited?
CVE-2021-42564 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 48.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-42564?
CVE-2021-42564 has a CVSS v3 base score of 5.4 (NVD).
How do I remediate CVE-2021-42564?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-42564, 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.

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