VulnerabilityPublished 20 Sep 2022Updated 29 May 2025

CVE-2022-39957: OWASP ModSecurity Core Rule Set · Protection Mechanism Failure

Affects OWASP ModSecurity Core Rule SetSource CVE Database V5

Not known to be exploited · CVSS 7.3 High : upgrade to 3.2.0 or 3.1.0 soon.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

7.3High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.9% chance of exploitation in 30 days – higher than 62% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.2.0, 3.1.0

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 20 Sep 2022
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade OWASP ModSecurity Core Rule Set to 3.2.0 or 3.1.0.

Affected software

Product	Affected	Fixed in
OWASP ModSecurity Core Rule Set	Affected >=3.0.0 <3.1.0 >=3.1.0 <3.2.0	Fixed in 3.1.0 3.2.0

AI-suggested

European organizations should prioritize upgrading their OWASP ModSecurity CRS installations to versions 3.2.2 or 3.3.3, which contain fixes addressing this response body bypass vulnerability. It is critical to verify that all ModSecurity deployments using affected CRS versions are identified through asset inventories and patch management systems. Additionally, organizations should audit their WAF configurations to ensure that response body inspection is enabled and functioning correctly, and consider implementing additional security layers such as runtime application self-protection (RASP) or enhanced logging to detect anomalous access patterns. Network-level monitoring and anomaly detection systems should be tuned to identify unusual Accept header usage or encoded response patterns that could indicate exploitation attempts. Regular security assessments and penetration tests should include checks for this bypass scenario. Finally, organizations should maintain awareness of updates from OWASP and ModSecurity communities and subscribe to relevant vulnerability advisories to respond promptly to emerging threats.

Description

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. 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.

Impact

For European organizations, this vulnerability poses a substantial risk, especially for those relying on the OWASP ModSecurity CRS to protect web applications from attacks such as unauthorized access, data leakage, and injection attacks. The bypass can allow attackers to access restricted resources without detection, potentially leading to data breaches, unauthorized data modification, or service disruption. Organizations in sectors with strict data protection regulations, such as finance, healthcare, and government, could face compliance violations and reputational damage if exploited. The vulnerability's ability to affect confidentiality, integrity, and availability simultaneously increases the risk profile. Since the CRS is widely used as a community-driven WAF rule set integrated into various ModSecurity deployments, many European enterprises and service providers could be impacted if they have not applied the recommended updates. The lack of required privileges or user interaction for exploitation further increases the threat, as attackers can remotely exploit this vulnerability without authentication.

CWE-693Protection Mechanism Failure (opens in a new tab)
Pillar weaknessOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
OWASP Cheat Sheets
Secure Design Principles (opens in a new tab)
Attack patterns
Accessing Functionality Not Properly Constrained by ACLs (opens in a new tab)
Cross Site Tracing (opens in a new tab)
Directory Indexing (opens in a new tab)
Using Malicious Files (opens in a new tab)
Encryption Brute Forcing (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 8 Jul 2025, 03:11 UTC

WeaknessesCWE-693

Technical details

References

Community reviews

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