CVE-2020-11996
A public proof of concept exists; no exploitation attested.
- Published2020-06-26
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 specially crafted sequence of HTTP/2 requests sent to Apache Tomcat 10.0.0-M1 to 10.0.0-M5, 9.0.0.M1 to 9.0.35 and 8.5.0 to 8.5.55 could trigger high CPU usage for several seconds. If a sufficient number of such requests were made on concurrent HTTP/2 connections, the server could become unresponsive.
Timeline
dates in UTC- 2020-06-2617:15CVE publishedNVD
- 2026-10-2319:23First public proof of conceptPoC-in-GitHub
- 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-2020-11996?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-11996?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 | ≥ 8.5.0, ≤ 8.5.55 | no fix published | NVD |
| 9.0 | ≥ 9.0.0, ≤ 9.0.35 | no fix published | NVD |
| 9.0 | = 9.0.0 | no fix published | NVD |
| 10.0 | = 10.0.0 | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 12.2 | = 12.2.0.1 | no fix published | NVD |
| 18.x | = 18c | no fix published | NVD |
| 19.x | = 19c | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 10.0 | ≥ 10.0.0-M1, < 10.0.0-M5 | 10.0.0-M5 | OSV |
| 9.0 | ≥ 9.0.0.M1, < 9.0.35 | 9.0.35 | OSV |
| 8.5 | ≥ 8.5.0, < 8.5.55 | 8.5.55 | OSV |
8 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
Detection
read 2026-10-23 19:23 UTC- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- 1 repository, unverifiedrusakovichma/tomcat-embed-core-9.0.31-CVE-2020-11996 PoC-in-GitHub
Sources
- CISA-ADPSSVC decisionnone2026-10-08
- OpenCVESSVC decisionnone—
- NVDCVSS 3.17.5read 2026-10-23
- NVDCVSS 2.05read 2026-10-23
- FIRST EPSSEPSS score26.7 %read 2026-10-23
- PoC-in-GitHubproof of concept1read 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
- 2020-06-26
- Last Modified
- 2026-10-08
- NVD status
- Modified
Frequently asked questions
What is CVE-2020-11996?
Is CVE-2020-11996 actively exploited?
What is the CVSS score for CVE-2020-11996?
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