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CVE-2022-39956

Partial rule set bypass in OWASP ModSecurity Core Rule Set for HTTP multipart requests using character encoding in the Content-Type or Content-Transfer-Encoding header

7.3 HighFix available

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
Low
Availability
Low

Exploit likelihood

1.21%Up 0.3 points since Sep 20, 2022
90%50%10%1%

What each source reports

CVE List Score used 7.3

Partial rule set bypass in OWASP ModSecurity Core Rule Set for HTTP multipart requests using character encoding in the Content-Type or Content-Transfer-Encoding header

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).

Record
CVE-2022-39956
CVSS 3.1
7.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Weakness
CWE-863
Updated
2026-11-02
EUVDEUVD-2022-42400 7.3

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).

Record
EUVD-2022-42400
CVSS 3.1
7.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Updated
2026-11-02
GitHub AdvisoriesGHSA-5xc6-pmr2-qj78 9.8

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP...

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).

Record
GHSA-5xc6-pmr2-qj78
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-116, CWE-863
Updated
2026-11-02
NVD 7.3

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).

Record
CVE-2022-39956
CVSS 3.1
7.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-863, CWE-116
Updated
2026-11-02
OSV 7.3

Partial rule set bypass in OWASP ModSecurity Core Rule Set for HTTP multipart requests using character encoding in the Content-Type or Content-Transfer-Encoding header

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).

Record
CVE-2022-39956
CVSS 3.1
7.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Weakness
CWE-863
Updated
2026-11-02
OSVDEBIAN-CVE-2022-39956 9.8

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).

Record
DEBIAN-CVE-2022-39956
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-03
Show 6 moreShow less
OSVOESA-2022-1964 9.8

mod_security_crs security update

The base rules are provided for mod_security by this package.

Security Fix(es):

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass by submitting a specially crafted HTTP Content-Type header field that indicates multiple character encoding schemes. A vulnerable back-end can potentially be exploited by declaring multiple Content-Type "charset" names and therefore bypassing the configurable CRS Content-Type header "charset" allow list. An encoded payload can bypass CRS detection this way and may then be decoded by the backend. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised to upgrade to 3.2.2 and 3.3.3 respectively.(CVE-2022-39955)

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).(CVE-2022-39956)

Record
OESA-2022-1964
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVOESA-2025-1559 9.8

mod_security security update

This software is also called Modsec,it is an open-source web application firewall. It is designed for Apache HTTP Server.ModSecurity is commonly deployed to provide protections against generic classed of vulnerabilities.The install of this package is easy and you can read the README.TXT for more information.

Security Fix(es):

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).(CVE-2022-39956)

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Versions up to and including 2.9.8 are vulnerable to denial of service in one special case (in stable released versions): when the payload's content type is application/json, and there is at least one rule which does a sanitiseMatchedBytes action. A patch is available at pull request 3389 and expected to be part of version 2.9.9. No known workarounds are available.(CVE-2025-47947)

Record
OESA-2025-1559
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVOESA-2025-1560 9.8

mod_security security update

This software is also called Modsec,it is an open-source web application firewall. It is designed for Apache HTTP Server.ModSecurity is commonly deployed to provide protections against generic classed of vulnerabilities.The install of this package is easy and you can read the README.TXT for more information.

Security Fix(es):

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).(CVE-2022-39956)

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Versions up to and including 2.9.8 are vulnerable to denial of service in one special case (in stable released versions): when the payload's content type is application/json, and there is at least one rule which does a sanitiseMatchedBytes action. A patch is available at pull request 3389 and expected to be part of version 2.9.9. No known workarounds are available.(CVE-2025-47947)

Record
OESA-2025-1560
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVOESA-2025-1561 9.8

mod_security security update

This software is also called Modsec,it is an open-source web application firewall. It is designed for Apache HTTP Server.ModSecurity is commonly deployed to provide protections against generic classed of vulnerabilities.The install of this package is easy and you can read the README.TXT for more information.

Security Fix(es):

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).(CVE-2022-39956)

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Versions up to and including 2.9.8 are vulnerable to denial of service in one special case (in stable released versions): when the payload's content type is application/json, and there is at least one rule which does a sanitiseMatchedBytes action. A patch is available at pull request 3389 and expected to be part of version 2.9.9. No known workarounds are available.(CVE-2025-47947)

Record
OESA-2025-1561
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2022-39956 7.3

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).

Record
UBUNTU-CVE-2022-39956
CVSS 3.1
7.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVMGASA-2024-0070 No score

Updated apache-mod_security-crs packages fix security vulnerabilities

A SQL injection bypass (aka PL1 bypass) exists in OWASP ModSecurity Core Rule Set (owasp-modsecurity-crs) through v3.1.0-rc3 via {ab} where a is a special function name (such as "if") and b is the SQL statement to be executed. (CVE-2018-16384) Modsecurity owasp-modsecurity-crs 3.2.0 (Paranoia level at PL1) has a SQL injection bypass vulnerability. Attackers can use the comment characters and variable assignments in the SQL syntax to bypass Modsecurity WAF protection and implement SQL injection attacks on Web applications. (CVE-2020-22669) OWASP ModSecurity Core Rule Set 3.1.x before 3.1.2, 3.2.x before 3.2.1, and 3.3.x before 3.3.2 is affected by a Request Body Bypass via a trailing pathname. (CVE-2021-35368) The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass by submitting a specially crafted HTTP Content-Type header field that indicates multiple character encoding schemes. A vulnerable back-end can potentially be exploited by declaring multiple Content-Type "charset" names and therefore bypassing the configurable CRS Content-Type header "charset" allow list. An encoded payload can bypass CRS detection this way and may then be decoded by the backend. (CVE-2022-39955) The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. (CVE-2022-39956) The OWASP ModSecurity Core Rule Set (CRS) is affected by a response body bypass. A client can issue an HTTP Accept header field containing an optional "charset" parameter in order to receive the response in an encoded form. Depending on the "charset", this response can not be decoded by the web application firewall. A restricted resource, access to which would ordinarily be detected, may therefore bypass detection. (CVE-2022-39957) The OWASP ModSecurity Core Rule Set (CRS) is affected by a response body bypass to sequentially exfiltrate small and undetectable sections of data by repeatedly submitting an HTTP Range header field with a small byte range. A restricted resource, access to which would ordinarily be detected, may be exfiltrated from the backend, despite being protected by a web application firewall that uses CRS. Short subsections of a restricted resource may bypass pattern matching techniques and allow undetected access. (CVE-2022-39958)

Record
MGASA-2024-0070
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
modsecurity-crs
Debian:12
before 3.3.4-1
3.3.4-1
modsecurity-crs
Debian:13
before 3.3.4-1
3.3.4-1
modsecurity-crs
Debian:14
before 3.3.4-1
3.3.4-1
modsecurity-crs
Debian:10
From an advisory covering 7 CVEs
before 3.2.3-0+deb10u3, plus listed versions
3.1.0-13.1.0-1+deb10u13.1.0-1+deb10u23.1.1-13.2.0-1
3.2.3-0+deb10u3
modsecurity-crs
Debian:11
From an advisory covering 5 CVEs
before 3.3.4-1~deb11u1, plus listed versions
3.3.0-13.3.0-1+deb11u13.3.2-1
3.3.4-1~deb11u1
apache-mod_security-crs
Mageia:9
From an advisory covering 7 CVEs
before 3.3.5-1.mga9
3.3.5-1.mga9
mod_security_crs
openEuler:20.03-LTS-SP1
From an advisory covering 2 CVEs
before 3.2.2-1.oe1
3.2.2-1.oe1
mod_security_crs
openEuler:20.03-LTS-SP3
From an advisory covering 2 CVEs
before 3.2.2-1.oe1
3.2.2-1.oe1
mod_security_crs
openEuler:22.03-LTS
From an advisory covering 2 CVEs
before 3.2.2-1.oe2203
3.2.2-1.oe2203
mod_security
openEuler:20.03-LTS-SP4
From an advisory covering 2 CVEs
before 2.9.9-1.oe2003sp4
2.9.9-1.oe2003sp4
Show 10 moreShow less
Affected packages
PackageAffectedFixed
mod_security
openEuler:22.03-LTS-SP3
From an advisory covering 2 CVEs
before 2.9.9-1.oe2203sp3
2.9.9-1.oe2203sp3
mod_security
openEuler:22.03-LTS-SP4
From an advisory covering 2 CVEs
before 2.9.9-1.oe2203sp4
2.9.9-1.oe2203sp4
modsecurity-crs
Ubuntu:16.04:LTS
All versions, plus listed versions
2.2.9-1
None known
modsecurity-crs
Ubuntu:18.04:LTS
All versions, plus listed versions
3.0.0-33.0.2-1
None known
modsecurity-crs
Ubuntu:20.04:LTS
All versions, plus listed versions
3.1.1-13.2.0-1
None known
modsecurity-crs
Ubuntu:22.04:LTS
All versions, plus listed versions
3.3.0-13.3.2-1
None known
modsecurity-crs
Ubuntu:24.04:LTS
All versions, plus listed versions
3.3.5-13.3.5-2
None known
modsecurity-crs
Ubuntu:25.10
All versions, plus listed versions
3.3.7-1
None known
modsecurity-crs
Ubuntu:26.10
All versions, plus listed versions
3.3.8-13.3.9-1
None known
modsecurity-crs
Ubuntu:26.04:LTS
All versions, plus listed versions
3.3.7-13.3.8-1
None known

History

History
RecordedChangedSources
affected, factsOSV
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2022-39956 is a high vulnerability (CVSS 7.3) in Owasp Modsecurity Core Rule Set, published September 20, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.21%, the 68th percentile. Fixed in modsecurity-crs 3.3.4-1.

References

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