CVE-2021-27850
published 2021-04-15CVE-2021-27850: A critical unauthenticated remote code execution vulnerability was found all recent versions of Apache Tapestry. The affected versions include 5.4.5, 5.5.0…
PriorityP191critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
ITWEXPLOITVulnCheck KEVInitial access
Exploited in the wild
EPSS
94.09%
99.8th percentile
A critical unauthenticated remote code execution vulnerability was found all recent versions of Apache Tapestry. The affected versions include 5.4.5, 5.5.0, 5.6.2 and 5.7.0. The vulnerability I have found is a bypass of the fix for CVE-2019-0195. Recap: Before the fix of CVE-2019-0195 it was possible to download arbitrary class files from the classpath by providing a crafted asset file URL. An attacker was able to download the file `AppModule.class` by requesting the URL `http://localhost:8080/assets/something/services/AppModule.class` which contains a HMAC secret key. The fix for that bug was a blacklist filter that checks if the URL ends with `.class`, `.properties` or `.xml`. Bypass: Unfortunately, the blacklist solution can simply be bypassed by appending a `/` at the end of the URL: `http://localhost:8080/assets/something/services/AppModule.class/` The slash is stripped after the blacklist check and the file `AppModule.class` is loaded into the response. This class usually contains the HMAC secret key which is used to sign serialized Java objects. With the knowledge of that key an attacker can sign a Java gadget chain that leads to RCE (e.g. CommonsBeanUtils1 from ysoserial). Solution for this vulnerability: * For Apache Tapestry 5.4.0 to 5.6.1, upgrade to 5.6.2 or later. * For Apache Tapestry 5.7.0, upgrade to 5.7.1 or later.
Affected
2 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| apache | tapestry | >= 5.4.0 < 5.6.2 | 5.6.2 |
| apache | tapestry | >= 5.7.0 < 5.7.1 | 5.7.1 |
Detection & IOCsextracted from sources · hover to see the quote
- →Detect HTTP GET requests to asset paths ending with `.class/` (trailing slash bypass of blacklist filter). The slash is stripped server-side after the blacklist check, allowing class file download. ↗
- →Alert on HTTP responses with Content-Type `application/java` to `/assets/` paths — indicates successful class file retrieval. ↗
- →Response body containing both 'configuration' and 'webtools' strings alongside a 200 status confirms successful AppModule.class exfiltration. ↗
- →After HMAC key extraction, watch for incoming deserialization payloads signed with the leaked key — particularly CommonsBeanUtils1 gadget chains from ysoserial. ↗
- →The HMAC key in AppModule.class follows UUID format: 6 hex digits - 4 hex digits - 4 hex digits - 4 hex digits - 12 hex digits. Use regex to detect key extraction attempts. ↗
- ·The vulnerability only affects Apache Tapestry versions 5.4.5, 5.5.0, 5.6.2, and 5.7.0. The Metasploit module will fail to extract the HMAC key if it has been changed from the default UUID format. ↗
- ·The blacklist fix for CVE-2019-0195 checked for URLs ending in `.class`, `.properties`, or `.xml` — this bypass appends a trailing `/` which evades the check before being stripped server-side. ↗
CVSS provenance
nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
nvdv2.010.0CRITICALAV:N/AC:L/Au:N/C:C/I:C/A:C
ghsa9.8CRITICAL
osv9.8CRITICAL
vulncheck9.8CRITICAL
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OSV
Remote code execution in Apache Tapestry
osv·2021-06-16·CVSS 9.8
CVE-2021-27850 [CRITICAL] Remote code execution in Apache Tapestry
Remote code execution in Apache Tapestry
A critical unauthenticated remote code execution vulnerability was found all recent versions of Apache Tapestry. The affected versions include 5.4.5, 5.5.0, 5.6.2 and 5.7.0. The vulnerability I have found is a bypass of the fix for CVE-2019-0195. Recap: Before the fix of CVE-2019-0195 it was possible to download arbitrary class files from the classpath by providing a crafted asset file URL. An attacker was able to download the file `AppModule.class` by requesting the URL `http://localhost:8080/assets/something/services/AppModule.class` which contains a HMAC secret key. The fix for that bug was a blacklist filter that checks if the URL ends with `.class`, `.properties` or `.xml`. Bypass: Unfortunately, the blacklist solution can simply be bypassed b
GHSA
Remote code execution in Apache Tapestry
ghsa·2021-06-16·CVSS 9.8
CVE-2021-27850 [CRITICAL] CWE-502 Remote code execution in Apache Tapestry
Remote code execution in Apache Tapestry
A critical unauthenticated remote code execution vulnerability was found all recent versions of Apache Tapestry. The affected versions include 5.4.5, 5.5.0, 5.6.2 and 5.7.0. The vulnerability I have found is a bypass of the fix for CVE-2019-0195. Recap: Before the fix of CVE-2019-0195 it was possible to download arbitrary class files from the classpath by providing a crafted asset file URL. An attacker was able to download the file `AppModule.class` by requesting the URL `http://localhost:8080/assets/something/services/AppModule.class` which contains a HMAC secret key. The fix for that bug was a blacklist filter that checks if the URL ends with `.class`, `.properties` or `.xml`. Bypass: Unfortunately, the blacklist solution can simply be bypassed b
VulnCheck
Apache tapestry Exposure of Sensitive Information to an Unauthorized Actor
vulncheck·2021·CVSS 9.8
CVE-2021-27850 [CRITICAL] Apache tapestry Exposure of Sensitive Information to an Unauthorized Actor
Apache tapestry Exposure of Sensitive Information to an Unauthorized Actor
A critical unauthenticated remote code execution vulnerability was found all recent versions of Apache Tapestry. The affected versions include 5.4.5, 5.5.0, 5.6.2 and 5.7.0. The vulnerability I have found is a bypass of the fix for CVE-2019-0195. Recap: Before the fix of CVE-2019-0195 it was possible to download arbitrary class files from the classpath by providing a crafted asset file URL. An attacker was able to download the file `AppModule.class` by requesting the URL `http://localhost:8080/assets/something/services/AppModule.class` which contains a HMAC secret key. The fix for that bug was a blacklist filter that checks if the URL ends with `.class`, `.properties` or `.xml`. Bypass: Unfortunately, the blacklist
No detection rules found.
Nuclei
Apache Tapestry - Remote Code Execution
nuclei·CVSS 9.8
CVE-2021-27850 [CRITICAL] Apache Tapestry - Remote Code Execution
Apache Tapestry - Remote Code Execution
Apache Tapestry contains a critical unauthenticated remote code execution vulnerability. Affected versions include 5.4.5, 5.5.0, 5.6.2 and 5.7.0. Note that this vulnerability is a bypass of the fix for CVE-2019-0195. Before that fix it was possible to download arbitrary class files from the classpath by providing a crafted asset file URL.
Template:
id: CVE-2021-27850
info:
name: Apache Tapestry - Remote Code Execution
author: pdteam
severity: critical
description: |
Apache Tapestry contains a critical unauthenticated remote code execution vulnerability. Affected versions include 5.4.5, 5.5.0, 5.6.2 and 5.7.0. Note that this vulnerability is a bypass of the fix for CVE-2019-0195. Before that fix it was possible to download arbitrary class files fr
Metasploit
Apache Tapestry HMAC secret key leak
metasploit
Apache Tapestry HMAC secret key leak
Apache Tapestry HMAC secret key leak
This exploit finds the HMAC secret key used in Java serialization by Apache Tapestry. This key is located in the file AppModule.class by default and looks like the standard representation of UUID in hex digits (hd) : 6hd-4hd-4hd-4hd-12hd If the HMAC key has been changed to look differently, this module won't find the key because it tries to download the file and then uses a specific regex to find the key.
Greynoiseio
U.S. and UK Warn of Russian Cyber Threats: 9 of 12 GreyNoise-Tracked Vulnerabilities in the Advisory Are Being Probed Right Now
blogs_greynoiseio·2024-10-17
U.S. and UK Warn of Russian Cyber Threats: 9 of 12 GreyNoise-Tracked Vulnerabilities in the Advisory Are Being Probed Right Now
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Why GreyNoise
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Unit42
Network Security Trends: May-July 2021
blogs_unit42·2021-09-17
Network Security Trends: May-July 2021
## Executive Summary
Unit 42 researchers continue to observe network security trends, tracking how cybercriminals take advantage of vulnerabilities in the real world. The following sections present our analysis of the most recently published vulnerabilities, including their severity and category distribution. Additionally, we provide insight into how the vulnerabilities are exploited in the wild based on real-world data collected from Palo Alto Networks Next-Generation Firewalls. We highlight vulnerabilities ranked medium severity and above that were newly published from May-July 2021 in order to raise awareness of their active exploits in the wild. We then draw conclusions about the most commonly exploited vulnerabilities we observed attackers using, as well as the severity, category and
Unit42
Network Security Trends: May-July 2021
blogs_unit42·2021-09-17
Network Security Trends: May-July 2021
Threat Research Center
Trend Reports
Vulnerabilities
## Network Security Trends: May-July 2021
Yue Guan
Lei Xu
Published: September 17, 2021
Malware
Trend Reports
Vulnerabilities
Attack analysis
Exploit
Exploit in the wild
Network security trends
## Executive Summary
Unit 42 researchers continue to observe network security trends, tracking how cybercriminals take advantage of vulnerabilities in the real world. The following sections present our analysis of the most recently published vulnerabilities, including their severity and category distribution. Additionally, we provide insight into how the vulnerabilities are exploited in the wild based on real-world data collected from Palo Alto Networks Next-Generation Firewalls . We highlight vulnerabilities ranked medium sever
http://www.openwall.com/lists/oss-security/2021/04/15/1https://lists.apache.org/thread.html/r237ff7f286bda31682c254550c1ebf92b0ec61329b32fbeb2d1c8751%40%3Cusers.tapestry.apache.org%3Ehttps://security.netapp.com/advisory/ntap-20210528-0002/http://www.openwall.com/lists/oss-security/2021/04/15/1https://lists.apache.org/thread.html/r237ff7f286bda31682c254550c1ebf92b0ec61329b32fbeb2d1c8751%40%3Cusers.tapestry.apache.org%3Ehttps://security.netapp.com/advisory/ntap-20210528-0002/
2021-04-15
Published
Exploited in the wild