CVE-2026-103866: Request Smuggling (CVSS 7.5)

Description

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.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS — Exploit Prediction

0.0033

Probability of exploitation

0.26%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-436 CWE-436

CWE-444 CWE-444

References

Other References

https://lists.apache.org/thread.html/yoftbty2lc7kmtldmyvj7w0m0n1ncbf6 http://www.openwall.com/lists/oss-security/2026/11/05/8

Frequently Asked Questions

What is CVE-2026-103866? +

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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-103866? +

CVE-2026-103866 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0033, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-103866? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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