# CVE-2021-28169: Eclipse Jetty - Information Disclosure

> Live exploitation tracking for CVE-2021-28169 by the CrowdSec Live Exploit Tracker, built from real-world attack data crowdsourced from CrowdSec's global network.

Page: https://tracker.crowdsec.net/cves/CVE-2021-28169

## Key facts

- **Exploitation phase:** Limited Exploitation. The vulnerability is known but shows very limited attacker interest or exploitation activity.
- **CVSS score:** 5.3
- **Public exploit available:** Yes
- **Affected products:** The Eclipse Foundation Eclipse Jetty
- **Weaknesses:** CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)
- **Tags:** web_server

## Description

For Eclipse Jetty versions <= 9.4.40, <= 10.0.2, <= 11.0.2, it is possible for requests to the ConcatServlet with a doubly encoded path to access protected resources within the WEB-INF directory. For example a request to `/concat?/%2557EB-INF/web.xml` can retrieve the web.xml file. This can reveal sensitive information regarding the implementation of a web application.

## CrowdSec analysis

[CVE-2021-28169](https://euvd.enisa.europa.eu/vulnerability/CVE-2021-28169) is a vulnerability in Eclipse Jetty that allows remote attackers to access protected resources within the WEB-INF directory by exploiting doubly encoded paths in requests to the ConcatServlet. This flaw can expose sensitive files such as web.xml, potentially revealing critical information about the web application's internal configuration and implementation.

CrowdSec has been tracking this vulnerability and its exploits since 10th of September 2025.

Insights from the CrowdSec network reveal that the attackers trying to exploit CVE-2021-28169 are composed of a fairly even mix of opportunistic and targeted actors. Some attackers employ preliminary reconnaissance, while others use indiscriminate scanning.
CrowdSec data also reveals a clear uptick in attacks involving CVE-2021-28169 over the past week. Activity is above the usual baseline, suggesting growing attention from attackers. This may reflect rising awareness, recent exploit releases, or expanded targeting efforts.

Attackers exploit this vulnerability by sending requests to endpoints such as `/static` or `/concat` with doubly encoded paths like `/%2557EB-INF/web.xml` to access sensitive files within the `WEB-INF` directory.

## Timeline

- 2021-06-09: CVE Published. CVE-2021-28169 is published to NVD.
- 2025-09-10: Rule Released. CrowdSec releases a rule to detect CVE-2021-28169 exploitation attempts against the CrowdSec Network.
- 2025-09-12: CrowdSec First Seen. CrowdSec observes in-the-wild exploitation of CVE-2021-28169 for the first time.

## References

- https://lists.apache.org/thread.html/rf36f1114e84a3379b20587063686148e2d5a39abc0b8a66ff2a9087a%40%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/rddbb4f8d5db23265bb63d14ef4b3723b438abc1589f877db11d35450%40%3Cissues.zookeeper.apache.org%3E
- https://github.com/eclipse/jetty.project/security/advisories/GHSA-gwcr-j4wh-j3cq
- https://lists.apache.org/thread.html/r234f6452297065636356f43654cdacef565b8f9ceb0e0c07ffb8c73b%40%3Cdev.kafka.apache.org%3E
- https://lists.apache.org/thread.html/ref1c161a1621504e673f9197b49e6efe5a33ce3f0e6d8f1f804fc695%40%3Cjira.kafka.apache.org%3E
- https://lists.apache.org/thread.html/rb1292d30462b9baedea7c5d9594fc75990d9aa0ec223b48054ca9c25%40%3Cjira.kafka.apache.org%3E
- https://lists.apache.org/thread.html/r91e34ff61aff8fd25a3f2a21539597c6ef7589a31c199b0a9546477c%40%3Cjira.kafka.apache.org%3E
- https://security.netapp.com/advisory/ntap-20210727-0009/
- https://lists.apache.org/thread.html/rfff6ff8ffb31e8a32619c79774def44b6ffbb037c128c5ad3eab7171%40%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/r04a4b4553a23aff26f42635a6ae388c3b162aab30a88d12e59d05168%40%3Cjira.kafka.apache.org%3E
- https://www.debian.org/security/2021/dsa-4949
- https://lists.debian.org/debian-lts-announce/2021/06/msg00017.html
- https://lists.apache.org/thread.html/r29678972c3f8164b151fd7a5802785d402e530c09870a82ffc7681a4%40%3Cdev.kafka.apache.org%3E
- https://lists.apache.org/thread.html/rd5b52362f5edf98e0dcab6541a381f571cccc05ad9188e793af688f3%40%3Cjira.kafka.apache.org%3E
- https://lists.apache.org/thread.html/r8a1a332899a1f92c8118b0895b144b27a78e3f25b9d58a34dd5eb084%40%3Cnotifications.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/r67c4f90658fde875521c949448c54c98517beecdc7f618f902c620ec%40%3Cissues.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/r32b0b640ad2be3b858f0af51c68a7d5c5a66a462c8bbb93699825cd3%40%3Cissues.zookeeper.apache.org%3E
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://lists.apache.org/thread.html/r33eb06b05afbc7df28d31055cae0cb3fd36cab808c884bf6d680bea5%40%3Cdev.zookeeper.apache.org%3E
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://lists.apache.org/thread.html/r2721aba31a8562639c4b937150897e24f78f747cdbda8641c0f659fe%40%3Cusers.kafka.apache.org%3E
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://lists.apache.org/thread.html/rbefa055282d52d6b58d29a79fbb0be65ab0a38d25f00bd29eaf5e6fd%40%3Cnotifications.zookeeper.apache.org%3E
- https://lists.apache.org/thread.html/r284de9c5399486dfff12ab9e7323ca720dd7019a9a3e11c8510a7140%40%3Cjira.kafka.apache.org%3E
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-28169.yaml

## Live exploitation data

The [Live Exploit Tracker page](https://tracker.crowdsec.net/cves/CVE-2021-28169) follows observed exploitation activity for CVE-2021-28169. [Request an API key](https://tracker.crowdsec.net/request-api-key) for full access to its exploitation timeline, attacking IP addresses and blocklists.