CVE-2021-30639
No exploitation reported by the sources we read.
- Published2021-07-12
- WeaknessCWE-755
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
Description
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.
Timeline
dates in UTC- 2021-07-1215:15CVE publishedNVD
Observed activity
isMalicious corpus · updated 2026-10-23 21:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-30639?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-30639?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD · OSV| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 8.5 | = 8.5.64 | no fix published | NVD |
| 9.0 | = 9.0.44 | no fix published | NVD |
| 10.0 | = 10.0.3 | no fix published | NVD |
| 10.0 | = 10.0.4 | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 10.0 | ≥ 10.0.4, < 10.0.5 | 10.0.5 | OSV |
| 10.0 | ≥ 10.0.3, < 10.0.4 | 10.0.4 | OSV |
| 9.0 | ≥ 9.0.44, < 9.0.45 | 9.0.45 | OSV |
| 8.5 | ≥ 8.5.64, < 8.5.65 | 8.5.65 | OSV |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 10.0 | ≥ 10.0.3, < 10.0.5 | 10.0.5 | OSV |
| 9.0 | ≥ 9.0.0, < 9.0.45 | 9.0.45 | OSV |
| 8.5 | < 8.5.65 | 8.5.65 | OSV |
2 more products in the sources.
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Fix
Advisories and patches
- lists.apache.orgVendor Advisory
- www.oracle.comPatch
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
- NVDCVSS 3.17.5read 2026-10-23
- NVDCVSS 2.05read 2026-10-23
- NVDweakness (CWE)CWE-755read 2026-10-23
- FIRST EPSSEPSS score6.9 %2026-10-23
- OSVaffected packages—
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Published
- 2021-07-12
- Last Modified
- 2026-06-17
- NVD status
- Modified
Frequently asked questions
What is CVE-2021-30639?
Is CVE-2021-30639 actively exploited?
What is the CVSS score for CVE-2021-30639?
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Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.