Security readout for executives and security teams
Plain-English summary
This issue weakens the OWASP ModSecurity Core Rule Set as a web application firewall layer. A crafted Content-Type header can bypass part of CRS character-set filtering, letting encoded malicious input reach a vulnerable backend that may decode it. It is a high-priority defense-in-depth issue, not proof that every protected application is directly exploitable.
Executive priority
Treat this as a high-priority WAF maintenance issue for internet-facing applications. It can reduce protection against malicious traffic, but sources do not establish active exploitation. Prioritize upgrades where CRS protects sensitive, authenticated, or business-critical web services.
Technical view
CVE-2022-39955 is a partial CRS rule bypass involving multiple charset declarations in the HTTP Content-Type header. Affected CRS branches include legacy 3.0.x and 3.1.x, plus supported 3.2.1 and 3.3.2. The documented fix path is upgrading to CRS 3.2.2 or 3.3.3 respectively.
Likely exposure
Organizations using OWASP ModSecurity CRS in front of web applications may be exposed, especially deployments on CRS 3.0.x, 3.1.x, 3.2.1, or 3.3.2. Practical risk depends on backend behavior and whether encoded requests are decoded and processed after bypassing CRS inspection.
Exploitation context
The CVSS vector indicates network access, low complexity, no privileges, and no user interaction. The source bundle does not show CISA KEV listing or cited evidence of active exploitation. This is mainly a WAF bypass that can enable attacks against already vulnerable backend logic.
Researcher notes
The key research question is parser differential behavior between CRS inspection and backend decoding. Evidence supports a partial charset allow-list bypass, but not universal application compromise. Validate exposure by version, CRS integration point, and backend content decoding behavior.
Mitigation direction
- Upgrade OWASP CRS 3.2.1 to 3.2.2 or 3.3.2 to 3.3.3.
- Replace legacy CRS 3.0.x and 3.1.x deployments with a supported fixed version.
- Apply distribution security updates for packaged modsecurity-crs where applicable.
- Review vendor advisories before relying on temporary configuration workarounds.
- Monitor web logs for unusual Content-Type charset patterns and blocked-rule anomalies.
Validation and detection
- Inventory all ModSecurity CRS versions across edge, reverse proxy, and application gateway deployments.
- Confirm packaged CRS versions include the vendor security update for CVE-2022-39955.
- Verify WAF regression tests cover Content-Type charset handling without exposing payload details.
- Check whether backend applications decode request bodies differently than CRS inspection expects.
- Review recent WAF bypass alerts and application errors around encoded request handling.
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-863: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. 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-2022-39955 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.
Incorrect Authorization
Incorrect Authorization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.