CVE-2021-30639

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 6.9%, top 7% 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
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 7%CVSS: 7.5Exploit: NoneExposed: 0

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

A vulnerability in Apache Tomcat allows an attacker to remotely trigger a denial of service. An error introduced as part of a change to improve error handling during non-blocking I/O meant that the error flag associated with the Request object was not reset between requests. This meant that once a non-blocking I/O error occurred, all future requests handled by that request object would fail. Users were able to trigger non-blocking I/O errors, e.g. by dropping a connection, thereby creating the possibility of triggering a DoS. Applications that do not use non-blocking I/O are not exposed to this vulnerability. This issue affects Apache Tomcat 10.0.3 to 10.0.4; 9.0.44; 8.5.64.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
—
EPSS
93.4%
KEV
Not listed

Published

July 12, 2021

Last Modified

November 21, 2024

References (14)

Affected Packages

(1 across 1 ecosystem)
Maven(1)
PackageVulnerable rangeFixed inDependents
org.apache.tomcat:tomcat7.0.100 ... 8.5.9 (149 versions)8.5.65—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 49× 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. 2026-07-22 22:47 UTCEG score recompute
  2. 2026-07-22 14:06 UTCEPSS rescore
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  69. 2026-05-26 13:56 UTCEG score recompute
  70. 2026-05-26 13:42 UTCEPSS rescore
  71. 2026-05-26 07:17 UTCEPSS rescore
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Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-30639?
CVE-2021-30639 is a high vulnerability published on July 12, 2021. A vulnerability in Apache Tomcat allows an attacker to remotely trigger a denial of service. An error introduced as part of a change to improve error handling during non-blocking I/O meant that the error flag associated with the Request object was not reset between requests. This meant that once a…
When was CVE-2021-30639 disclosed?
CVE-2021-30639 was first published in the National Vulnerability Database on July 12, 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-2021-30639 actively exploited?
CVE-2021-30639 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 93.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-30639?
CVE-2021-30639 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2021-30639?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-30639, 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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