CVE-2021-27850
Published Apr 15, 2021
Last updated 3 years ago
Overview
- Description
- 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.
- Source
- security@apache.org
- NVD status
- Analyzed
Social media
- Hype score
- Not currently trending
Risk scores
CVSS 3.1
- Type
- Primary
- Base score
- 9.8
- Impact score
- 5.9
- Exploitability score
- 3.9
- Vector string
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Severity
- CRITICAL
CVSS 2.0
- Type
- Primary
- Base score
- 10
- Impact score
- 10
- Exploitability score
- 10
- Vector string
- AV:N/AC:L/Au:N/C:C/I:C/A:C
Configurations
[
{
"nodes": [
{
"negate": false,
"cpeMatch": [
{
"criteria": "cpe:2.3:a:apache:tapestry:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "5611789E-E882-49FF-9E33-A8612A394FE5",
"versionEndExcluding": "5.6.2",
"versionStartIncluding": "5.4.0"
},
{
"criteria": "cpe:2.3:a:apache:tapestry:*:*:*:*:*:*:*:*",
"vulnerable": true,
"matchCriteriaId": "4709FF63-6606-413B-941E-3E58DDA96203",
"versionEndExcluding": "5.7.1",
"versionStartIncluding": "5.7.0"
}
],
"operator": "OR"
}
]
}
]