What is CVE-2026-15396?

CVE-2026-15396 is a medium-severity vulnerability in IBM Websphere Application Server, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 6.5/10. Published 2026-09-14.

How severe is CVE-2026-15396?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in IBM Websphere Application Server

CVE-2026-15396

IBM WebSphere Application Server 9.0, and 8.5 and IBM WebSphere Application Server - Liberty are vulnerable to HTTP request smuggling, caused by improper parsing of the HTTP transfer-encoding request header. By sending a specially crafted HTTP transfer-encoding request header, an attacker could exploit this vulnerability to poison the web cache, bypass web application firewall protection, and conduct XSS attacks.

Vulnerability class: HTTP Request Smuggling

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.

Affected products

Ibm Websphere Application Server — versions 8.5, 9.0

Weakness classification (CWE)

CWE-444 — Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling)

References

psirt@us.ibm.com (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-15396?: CVE-2026-15396 is a medium-severity vulnerability in IBM Websphere Application Server, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 6.5/10. Published 2026-09-14.
How severe is CVE-2026-15396?: Medium severity. CVSS v3 base score is 6.5 out of 10.