CVE-2022-39957Network attack vector

Restricted-resource access via undecodable charset responses

Published Sep 20, 2022 · Updated Nov 3, 2025

Response inspection bypass in OWASP Core Rule Set 3.0.x, 3.1.x, 3.2.1, and 3.3.2 allows remote attackers to access restricted resources. An Accept header with an optional charset parameter makes the origin encode its response in a character set the WAF cannot decode, so CRS does not inspect the response body. The target must expose a protected resource that honors the requested charset; the bypass can disclose response data without reported code execution or service interruption.

CVSS severity7.3
High
EPSS probability0.82%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Response inspection bypass in OWASP Core Rule Set 3.0.x, 3.1.x, 3.2.1, and 3.3.2 allows remote attackers to access restricted resources. An Accept header with an optional charset parameter makes the origin encode its response in a character set the WAF cannot decode, so CRS does not inspect the response body. The target must expose a protected resource that honors the requested charset; the bypass can disclose response data without reported code execution or service interruption.

The record

CVE
CVE-2022-39957
Published
Sep 20, 2022
Updated
Nov 3, 2025
Vendor
OWASP Foundation
Product
OWASP Core Rule Set
Classifications
CWE-116, CWE-693, T1027
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 20, 2022CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.0.x
  2. Affected versionversion=3.1.x
  3. Affected versionversion=unspecified <=3.2.1
  4. Affected versionversion=unspecified <=3.3.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OWASP Foundation · OWASP Core Rule Setversion=3.0.x; version=3.1.x; version=unspecified <=3.2.1; version=unspecified <=3.3.2

Published CVSS scores

7.3Switzerland Government Common Vulnerability ProgramCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
7.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-116Improper Encoding or Escaping of Output
CWE-693Protection Mechanism Failure
T1027Obfuscated Files or Information

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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