CVE-2021-42340
No exploitation reported by the sources we read.
- Published2021-10-14
- Fixed in10.1.0-M6 · 10.0.12 · 9.0.54 · 8.5.72
- WeaknessCWE-772
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
The fix for bug 63362 present in Apache Tomcat 10.1.0-M1 to 10.1.0-M5, 10.0.0-M1 to 10.0.11, 9.0.40 to 9.0.53 and 8.5.60 to 8.5.71 introduced a memory leak. The object introduced to collect metrics for HTTP upgrade connections was not released for WebSocket connections once the connection was closed. This created a memory leak that, over time, could lead to a denial of service via an OutOfMemoryError.
Timeline
dates in UTC- 2021-10-1420:15CVE publishedNVD
- 2026-10-2319:23EPSS crossed 10 %FIRST EPSS
Observed activity
isMalicious corpus · updated 2026-10-23 21:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-42340?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-42340?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
OSV · NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 10.1 | ≥ 10.1.0-M1, < 10.1.0-M6 | 10.1.0-M6 | OSV |
| 10.0 | ≥ 10.0.1, < 10.0.12 | 10.0.12 | NVD · OSV |
| 10.0 | ≥ 10.0.0-M1, < 10.0.12 | 10.0.12 | OSV |
| 9.0 | ≥ 9.0.40, < 9.0.54 | 9.0.54 | NVD · OSV |
| 8.5 | ≥ 8.5.60, < 8.5.72 | 8.5.72 | NVD · OSV |
| 10.0 | = 10.0.0 | no fix published | NVD |
| 10.1 | = 10.1.0 | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 14.0 | = 14.0.4.13 | no fix published | NVD |
| 14.1 | = 14.1.3.5 | no fix published | NVD |
| 14.1 | = 14.1.3.14 | no fix published | NVD |
| 15.0 | = 15.0.3.3 | no fix published | NVD |
| 15.0 | = 15.0.3.8 | no fix published | NVD |
| 16.0 | = 16.0.3.7 | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 12.2 | = 12.2.1.3.0 | no fix published | NVD |
| 12.2 | = 12.2.1.4.0 | no fix published | NVD |
15 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
- Update Apache Tomcat to 10.1.0-M6 · 10.0.12 · 9.0.54 · 8.5.72
Advisories and patches
- lists.apache.orgVendor Advisory
- www.oracle.comPatch
- www.oracle.comPatch
- 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
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
- 2021-10-14
- Last Modified
- 2026-06-17
- NVD status
- Modified
Frequently asked questions
What is CVE-2021-42340?
Is CVE-2021-42340 actively exploited?
What is the CVSS score for CVE-2021-42340?
Running Apache Tomcat? Hear about its next vulnerability
Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».
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Go further
- Following what attackers exploit right now? The CISA KEV additions of the month, with their patch deadlines.
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Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.