UBUNTU-CVE-2026-21876

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Source
https://ubuntu.com/security/CVE-2026-21876
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21876.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-21876
Upstream
Published
2026-01-08T14:15:00Z
Modified
2026-01-14T21:53:43.859785Z
Severity
  • 9.3 (Critical) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

The OWASP core rule set (CRS) is a set of generic attack detection rules for use with compatible web application firewalls. Prior to versions 4.22.0 and 3.3.8, the current rule 922110 has a bug when processing multipart requests with multiple parts. When the first rule in a chain iterates over a collection (like MULTIPART_PART_HEADERS), the capture variables (TX:0, TX:1) get overwritten with each iteration. Only the last captured value is available to the chained rule, which means malicious charsets in earlier parts can be missed if a later part has a legitimate charset. Versions 4.22.0 and 3.3.8 patch the issue.

References

Affected packages

Ubuntu:16.04:LTS

modsecurity-crs

Package

Name
modsecurity-crs
Purl
pkg:deb/ubuntu/modsecurity-crs@2.2.9-1?arch=source&distro=xenial

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

2.*

2.2.9-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "modsecurity-crs",
            "binary_version": "2.2.9-1"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21876.json"

Ubuntu:18.04:LTS

modsecurity-crs

Package

Name
modsecurity-crs
Purl
pkg:deb/ubuntu/modsecurity-crs@3.0.2-1?arch=source&distro=bionic

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*

3.0.0-3
3.0.2-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "modsecurity-crs",
            "binary_version": "3.0.2-1"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21876.json"

Ubuntu:20.04:LTS

modsecurity-crs

Package

Name
modsecurity-crs
Purl
pkg:deb/ubuntu/modsecurity-crs@3.2.0-1?arch=source&distro=focal

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*

3.1.1-1
3.2.0-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "modsecurity-crs",
            "binary_version": "3.2.0-1"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21876.json"

Ubuntu:22.04:LTS

modsecurity-crs

Package

Name
modsecurity-crs
Purl
pkg:deb/ubuntu/modsecurity-crs@3.3.2-1?arch=source&distro=jammy

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*

3.3.0-1
3.3.2-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "modsecurity-crs",
            "binary_version": "3.3.2-1"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21876.json"

Ubuntu:24.04:LTS

modsecurity-crs

Package

Name
modsecurity-crs
Purl
pkg:deb/ubuntu/modsecurity-crs@3.3.5-2?arch=source&distro=noble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*

3.3.5-1
3.3.5-2

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "modsecurity-crs",
            "binary_version": "3.3.5-2"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21876.json"

Ubuntu:25.04

modsecurity-crs

Package

Name
modsecurity-crs
Purl
pkg:deb/ubuntu/modsecurity-crs@3.3.7-1?arch=source&distro=plucky

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*

3.3.5-2
3.3.6-1
3.3.7-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "modsecurity-crs",
            "binary_version": "3.3.7-1"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21876.json"

Ubuntu:25.10

modsecurity-crs

Package

Name
modsecurity-crs
Purl
pkg:deb/ubuntu/modsecurity-crs@3.3.7-1?arch=source&distro=questing

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

3.*

3.3.7-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "modsecurity-crs",
            "binary_version": "3.3.7-1"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-21876.json"