CVE-2021-23937DNS proxy and possible amplification attack
- 7.5HighCVSS base score
- 4.3%Exploitation in 30 daysEPSS · top 8.8% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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
ID reserved
By apache
- 4 months later
· 4 months later
Published
- 3 years later
· 3 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 4.3% · top 8.8% of all CVEs (12 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Affected products
Apache Software Foundation · Apache Wicket
- affected Apache Wicket 9.x – ≤ 9.2.0
- affected Apache Wicket 8.x – ≤ 8.11.0
- affected Apache Wicket 7.x – ≤ 7.17.0
- affected 6.2.0 – < Apache Wicket 6.x*
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Mavenorg.apache.wicket:wicket-coreGHSA-hmhg-95wh-r699 (opens in a new tab)
What to do
Workaround: Sanitize the X-Forwarded-For header by running an Apache Wicket application behind a reverse HTTP proxy. This proxy should put the client IP address in the X-Forwarded-For header and not pass through the contents of the header as received by the client.
References
References4
- https://lists.apache.org/thread.html/rc2ef22f90793e158cef65a7e370cdbca023c499d1403d65feeca870d%40%3Cusers.wicket.apache.org%3E (opens in a new tab)x_refsource_MISCx_transferred
- [wicket-announce] 20210526 Re: CVE-2021-23937: Apache Wicket: DNS proxy and possible amplification attack (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- [wicket-users] 20210526 Re: CVE-2021-23937: Apache Wicket: DNS proxy and possible amplification attack (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- [wicket-dev] 20210526 Re: CVE-2021-23937: Apache Wicket: DNS proxy and possible amplification attack (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2022-4175 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-hmhg-95wh-r699 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2021-23937)Record last updated .