Security readout for executives and security teams
Plain-English summary
This is a WAF detection bypass in OWASP ModSecurity CRS. A crafted HTTP Accept header can make protected response content appear in an encoding the WAF cannot decode, so access to restricted resources may evade CRS detection. It does not by itself prove backend compromise, but weakens a security control many organizations rely on.
Executive priority
Treat this as a high-priority control-bypass fix for systems depending on ModSecurity CRS. It may not equal direct application compromise, but it can reduce visibility and enforcement around sensitive web resources, undermining a compensating control.
Technical view
CRS response body inspection can fail when a client supplies an Accept header with an optional charset parameter that causes undecodable response content. Affected versions include legacy 3.0.x and 3.1.x, plus supported 3.2.1 and 3.3.2. The CVSS 3.1 score is 7.3, mapped to CWE-693 protection mechanism failure.
Likely exposure
Exposure is likely where OWASP ModSecurity CRS is deployed as a web application firewall and running affected CRS versions, including distribution-packaged modsecurity-crs installations. The issue matters most for applications relying on CRS response inspection to detect or block restricted-resource access.
Exploitation context
The provided sources do not show CISA KEV listing or confirmed active exploitation. The vulnerability is network-reachable, requires no privileges or user interaction, and has low attack complexity, but the supplied evidence only supports bypass potential, not observed exploitation.
Researcher notes
Evidence supports a response body bypass triggered through charset negotiation in the HTTP Accept header. The source bundle names fixed CRS releases but does not include exploit code, detailed payloads, or proof of active exploitation. Validate exposure by version and deployment role, not product name alone.
Mitigation direction
- Upgrade CRS 3.2.1 to 3.2.2 or CRS 3.3.2 to 3.3.3.
- Replace legacy CRS 3.0.x or 3.1.x deployments with a supported fixed release.
- Apply vendor distribution security updates for Fedora, Debian LTS, or Gentoo packages where relevant.
- Check OWASP CRS and operating-system vendor guidance for any environment-specific instructions.
- Prioritize internet-facing services where CRS protects restricted resources or sensitive response inspection.
Validation and detection
- Inventory all ModSecurity CRS deployments and record exact CRS versions.
- Confirm installed packages include the vendor security update or fixed CRS release.
- Review WAF configuration to confirm CRS response body inspection is expected on protected routes.
- Compare application and WAF logs for restricted-resource responses that were not detected.
- Document any unsupported legacy CRS instances as remediation exceptions until upgraded.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-693: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2022-39957 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L3.93.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.3HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Source materials
- CVE List V5 sourceCVE List V5
- https://coreruleset.org/20220919/crs-version-3-3-3-and-3-2-2-covering-several-cves/CVE reference
- FEDORA-2022-90708b46e3CVE reference · vendor-advisory
- FEDORA-2022-85a85c84b3CVE reference · vendor-advisory
- FEDORA-2022-1fd73a5285CVE reference · vendor-advisory
- [debian-lts-announce] 20230130 [SECURITY] [DLA 3293-1] modsecurity-crs security updateCVE reference · mailing-list
- GLSA-202305-25CVE reference · vendor-advisory
- https://lists.debian.org/debian-lts-announce/2025/08/msg00004.htmlCVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Protection Mechanism Failure
Protection Mechanism Failure represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.