CVSS 3.1
7.5 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:NCVE-2026-103866
High (7.5) in apache software foundation apache sling engine. EPSS 0.2% estimated probability of exploitation activity in the next 30 days.
On this page
Inconsistent interpretation of HTTP requests ('HTTP Request/Response smuggling') vulnerability in Apache Sling Engine. The engine's query/form parser accepts non-standard percent-escapes, wrong charsets, and continues request processing on such errors.
This issue affects Apache Sling Engine: before 3.0.4.
Users are recommended to upgrade to version 3.0.4, which fixes the issue.
Severity
- EPSS
- 0.2% estimated probability of exploitation activity in the next 30 days; 12th percentile. Scored 2026-11-10. A forecast for this CVE across the internet, not for your own systems.
- CISA's assessment (SSVC)
- Exploitation: none · Automatable: yes · Technical impact: partial, assessed 2026-11-10. From CISA's Vulnrichment in the CVE List: whether it is exploited, whether exploiting it can be automated, and how much control it gives.
- CWEs
- CWE-436 Interpretation Conflict
CWE-444 Inconsistent Interpretation of HTTP Requests (HTTP Request Smuggling) - OWASP Top 10
- A06:2025 Insecure Design
- Published
- Modified
- Assigned by
- apache (CNA)
- NVD analysis
- Awaiting analysis
- Record from
- the NVD, synced
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Affected
- apache software foundation:apache sling engine
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| Apache Software Foundation Apache Sling Engine | before 3.0.4 |
Red Hat
Red Hat rates this Low.
This vulnerability is rated with Low severity because successful HTTP request smuggling requires a specific proxy-to-backend architecture with mismatched request parsing behavior and timing conditions to achieve limited manipulation of adjacent requests. In typical Red Hat deployments, Apache Sling is rarely deployed as a directly exposed public frontend, and exploitation relies on fronting infrastructure forwarding malformed query strings or encoding anomalies rather than rejecting them at the perimeter. Because the underlying flaw does not permit arbitrary code execution, confidential data disclosure, or direct privilege escalation on the host system, the overall security risk remains low.
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Contains Red Hat Security Data © Red Hat, Inc., licensed under CC BY 4.0. Source: https://access.redhat.com/security/data. Modified: reformatted. Red Hat's page for CVE-2026-103866.
Attack patterns (CAPEC)
- CAPEC-33 HTTP Request Smuggling Likelihood: Medium · Severity: High
- CAPEC-273 HTTP Response Smuggling Likelihood: Medium · Severity: High
- CAPEC-34 HTTP Response Splitting Likelihood: Medium · Severity: High
- CAPEC-105 HTTP Request Splitting Likelihood: Medium · Severity: High
The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.
History
- Scored 7.5 high
Changes since this site first stored the record. The same for every record: /api/public/changes.