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K
zdtChristian Folini1337DAY-ID-34942
HistorySep 16, 2020 - 12:00 a.m.

ModSecurity 3.0.x Denial Of Service Vulnerability

2020-09-1600:00:00
Christian Folini
0day.today
22

7.5 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

5 Medium

CVSS2

Access Vector

Access Complexity

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

PARTIAL

AV:N/AC:L/Au:N/C:N/I:N/A:P

0.017 Low

EPSS

Percentile

87.8%

ModSecurity version 3.0.x suffers from a denial of service vulnerability due to the handling of regular expression matching. ModSecurity version 3.0.x is affected by a denial of service vulnerability due to the global matching of regular expressions. The combination of a non-anchored regular expression and the ModSecurity capture action can be exploited via a specially crafted payload.

ModSecurity v3.0.x is affected by a Denial of Service vulnerability due to the
global matching of regular expressions. The combination of a non-anchored
regular expression and the ModSecurity β€œcapture” action can be exploited via a
specially crafted payload.

While ModSecurity v2.x used to quit the execution of a regular expression
after the first match. ModSecurity v3.0.x silently changed the behavior to
global matching. This results in a DoS for existing non-anchored regexes in
rules containing the β€œcapture” action. It also fills the TX variable space
beyond the documented limit of 10 instances. The defense is handicapped due to
the absence of the SecRequestBodyNoFilesLimit directive. The vendor Trustwave
Spiderlabs dropped this functionality for ModSecurity v3.

The vendor did not publish a new release, but there is a patch that brings
back the former behavior.

CVSSv3: 7.5 HIGH 

https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H&version=3.1

Exploitability Metrics:
* Attack Vector: Network
* Attack Complexity: Low
* Priviledges Required: None
* User Interaction: None
* Scope: Unchanged
Impact Metrics:
* Confidentiality Impact: None
* Integrity Impact: None
* Availability Impact: High

Weakness Enumeration: CWE-400: Uncontrolled Resource Consumption

Known Affected Software Configurations:

    ModSecurity v3.0.0
    ModSecurity v3.0.1
    ModSecurity v3.0.2
    ModSecurity v3.0.3
    ModSecurity v3.0.4 (patch for this version available

More Information: https://coreruleset.org/20200914/cve-2020-15598/

7.5 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

5 Medium

CVSS2

Access Vector

Access Complexity

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

PARTIAL

AV:N/AC:L/Au:N/C:N/I:N/A:P

0.017 Low

EPSS

Percentile

87.8%