CVE-2022-39956: The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests

This month

HIGH 7.3REMOTEWATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2022-39956 is a high-severity flaw (CVSS 7.3) affecting owasp modsecurity core rule set, fedora, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 suppor

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.3 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.2% (top 32%)
CISA exploited list	No
Weakness	CWE-863, CWE-116
Published	2022-09-20
Last modified	2026-06-17

Publisher (CNA): Switzerland Government Common Vulnerability Program · Vendor: debian · fedoraproject · owasp

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-09-20 07:15 UTCPublished CVE record published
2026-06-17 04:58 UTCUpdated Record last modified

owasp owasp modsecurity core rule set UPGRADE

Affected: >= 3.0.0 and < 3.2.2 · >= 3.3.0 and < 3.3.3

Fixed in: 3.2.2, 3.3.3

Safe to downgrade to: a release before 3.0.0

1. Check installed version

apt-cache policy owasp-modsecurity-core-rule-set || rpm -q owasp-modsecurity-core-rule-set || owasp-modsecurity-core-rule-set --version

2. UPGRADE to 3.2.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade owasp-modsecurity-core-rule-set

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade owasp-modsecurity-core-rule-set

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.0.0 (Debian / Ubuntu)

apt-cache madison owasp-modsecurity-core-rule-set sudo apt install owasp-modsecurity-core-rule-set=<VERSION_BEFORE_3.0.0> sudo apt-mark hold owasp-modsecurity-core-rule-set

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list owasp-modsecurity-core-rule-set sudo dnf downgrade owasp-modsecurity-core-rule-set-<VERSION_BEFORE_3.0.0> sudo dnf versionlock add owasp-modsecurity-core-rule-set

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

fedoraproject fedora MITIGATE

Affected: 35 · 36 · 37

Fixed in: no fixed release known

Safe to downgrade to: a release before 35

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

debian debian linux MITIGATE

Affected: 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2022-39956?

owasp modsecurity core rule set: upgrade to 3.2.2, 3.3.3; fedora: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2022-39956 being exploited?

CVE-2022-39956 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2022-39956 affect?

CVE-2022-39956 affects owasp modsecurity core rule set, fedora, debian linux. Severity is high (CVSS 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 mu

How urgent is CVE-2022-39956?

Priority 53/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Debian vulnerabilities

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References

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