CVE-2026-103866: HTTP request smuggling via malformed query and form parsing
Not in the CISA KEV catalog. Low advisory severity (CVSS 3.7, Red Hat).
Compare the source-linked records below. Ratings and product/version details belong to each advisory; they are not a single CVE-wide score or proof that every listed product is affected. How VulniPulse collects and checks evidence.
CVE-2026-103866 key facts
- CISA KEV
- Not listed (catalog checked )
- Highest advisory severity
- Low
- CVSS base score
- 3.7 (Red Hat)
- Weakness
- CWE-444
- Fixed releases
- Apache: 3.0.4
- VulniPulse record
- Published · Updated
Scores, vectors, weaknesses and fixed releases are quoted from vendor advisories that cover only CVE-2026-103866; bulletin-wide values are not repeated here.
Is CVE-2026-103866 exploited?
No exploitation is reported in the sources VulniPulse tracks: CVE-2026-103866 is not in the CISA KEV catalog (checked ) and no tracked advisory for it reports exploitation. That is not proof the vulnerability cannot be exploited.
How do I fix CVE-2026-103866?
Upgrade to a fixed release named by the vendor:
- Apache: 3.0.4
- Users are recommended to upgrade to version 3.0.4, which fixes the issue. (Apache)
- 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. (Red Hat)
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Vendor advisory comparison
Apache
1 advisory- Advisory severityUnrated
Advisory [CVE-2026-103866] Inconsistent interpretation of HTTP requests ('HTTP Request/Response smuggling') vulnerability in Apache Sling Engine
CVE-2026-103866Source published Source updated
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.
- Affected products in this advisory
- Apache Sling Engine
- Source-reported affected versions
- Apache Sling Engine before 3.0.4
- Source-reported fixed versions
- 3.0.4
- Mitigation guidance
- Users are recommended to upgrade to version 3.0.4, which fixes the issue.
Red Hat
1 advisory- Advisory severityLow3.7
Low [CVE-2026-103866] HTTP request smuggling via malformed query and form parsing
CVE-2026-103866Source published Source updated
HTTP request smuggling via malformed query and form parsing. Red Hat rates this low (CVSS 3.7). Weakness: CWE-444.
- Related products — impact not confirmed
- No product details extracted. Check the source bulletin.
- Source-reported affected versions
- Affected-version details not available in this record.
- Source-reported fixed versions
- No fixed-version detail extracted. This does not mean no fix exists.
- Mitigation guidance
- 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.
More Apache advisories
- CVE-2026-103864Nov 5, 2026Improper output neutralization for logs in Apache Sling Engine
- CVE-2026-103863Nov 5, 2026Apache Sling Engine cross-site scripting (XSS)
- CVE-2026-90436Nov 6, 2026** UNSUPPORTED WHEN ASSIGNED ** Deserialization of an inbound SOAP fault in Apache Axis
- CVE-2026-85111Nov 6, 2026Apache James denial of service
- CVE-2026-85108Nov 6, 2026Apache James Mime4J denial of service
- CVE-2026-76168Nov 6, 2026In Apache James server prior version 3.9.1 relying on the SieveFileRepository incorect
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