CVE-2021-23937
No exploitation reported by the sources we read.
- Published2021-05-25
- WeaknessCWE-200
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 DNS proxy and possible amplification attack vulnerability in WebClientInfo of Apache Wicket allows an attacker to trigger arbitrary DNS lookups from the server when the X-Forwarded-For header is not properly sanitized. This DNS lookup can be engineered to overload an internal DNS server or to slow down request processing of the Apache Wicket application causing a possible denial of service on either the internal infrastructure or the web application itself. This issue affects Apache Wicket Apache Wicket 9.x version 9.2.0 and prior versions; Apache Wicket 8.x version 8.11.0 and prior versions; Apache Wicket 7.x version 7.17.0 and prior versions and Apache Wicket 6.x version 6.2.0 and later versions.
Timeline
dates in UTC- 2021-05-2517:15CVE 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-2021-23937?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-23937?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 |
|---|---|---|---|
| 6.x | ≥ 6.0.0, ≤ 6.2.0 | no fix published | NVD |
| 7.x | ≥ 7.0.0, ≤ 7.17.0 | no fix published | NVD |
| 8.x | ≥ 8.0.0, ≤ 8.11.0 | no fix published | NVD |
| 9.x | ≥ 9.0.0, ≤ 9.2.0 | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 9.x | ≥ 9.0.0, < 9.3.0 | 9.3.0 | OSV |
| 8.x | ≥ 8.0.0, < 8.12.0 | 8.12.0 | OSV |
| 7.18 | < 7.18.0 | 7.18.0 | OSV |
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.orgRelease Notes · Vendor Advisory
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-200read 2026-10-23
- FIRST EPSSEPSS score4.3 %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
- 2021-05-25
- Last Modified
- 2026-06-17
- NVD status
- Modified
Frequently asked questions
What is CVE-2021-23937?
Is CVE-2021-23937 actively exploited?
What is the CVSS score for CVE-2021-23937?
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