5.8

CVSS Score

3.0

-

CVSS Score

Basic Information

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CVE-2020-2100

CVE-2020-2100: Jenkins vulnerable to UDP amplification reflection attack

Jenkins 2.218 and earlier, LTS 2.204.1 and earlier supports two network discovery services (UDP multicast/broadcast and DNS multicast) by default.

The UDP multicast/broadcast service can be used in an amplification reflection attack, as very few bytes sent to the respective endpoint result in much larger responses: A single byte request to this service would respond with more than 100 bytes of Jenkins metadata which could be used in a DDoS attack on a Jenkins controller. Within the same network, spoofed UDP packets could also be sent to make two Jenkins controllers go into an infinite loop of replies to one another, thus causing a denial of service.

Jenkins 2.219, LTS 2.204.2 now disables both UDP multicast/broadcast and DNS multicast by default.

Administrators that need these features can re-enable them again by setting the system property hudson.DNSMultiCast.disabled to false (for DNS multicast) or the system property hudson.udp to 33848, or another port (for UDP broadcast/multicast). These are the same system properties that controlled whether these features were enabled in the past, so any instances explicitly enabling these features by setting these system properties will continue to have them enabled.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2020-2100

CVE-2020-2100:

5.8

CVSS Score

3.0

-

CVSS Score

Basic Information

Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
org.jenkins-ci.main:jenkins-core	maven	< 2.204.2	2.204.2
org.jenkins-ci.main:jenkins-core	maven	>= 2.205, < 2.219	2.219

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability stems from two network discovery services being enabled by default. The DNSMultiCast.disabled flag and UDPBroadcastThread.PORT initialization controlled these services. In vulnerable versions, DNSMultiCast.disabled defaulted to false (enabling DNS multicast) and UDPBroadcastThread.PORT defaulted to 33848 (enabling UDP). The commit diff shows these defaults were changed to 'true' and '-1' respectively to disable services by default. The static initializers for these variables directly controlled the vulnerable behavior.

Vulnerable functions

Only Mi**o us*rs **n s** t*is s**tion

WAF Protection Rules

WAF Rule

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Reasoning

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5.8

-

Basic Information

Basic Information

Concerned about an active attack path?

CVE-2020-2100: Jenkins vulnerable to UDP amplification reflection attack

CVE-2020-2100:

5.8

-

Basic Information

Basic Information

Technical Details

Technical Details

Vulnerability IntelligenceMiggo AI

Root Cause Analysis

Vulnerable functions

WAF Protection Rules

WAF Rule

Reasoning

Vulnerability IntelligenceMiggo AI

Basic Information

Basic Information

5.8

5.8

CVE-2020-2100: Jenkins vulnerable to UDP amplification reflection attack

Vulnerability IntelligenceMiggo AI

Root Cause Analysis

Vulnerable functions

WAF Protection Rules

WAF Rule

Reasoning

Technical Details

Vulnerability Intelligence
Miggo AI

Vulnerability Intelligence
Miggo AI

Vulnerability Intelligence
Miggo AI