CVE-2026-15634: Request Smuggling (CVSS 6.5)

Description

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.

Is your site exposed to CVE-2026-15634?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

6.5

MEDIUM

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

EPSS — Exploit Prediction

0.0025

Probability of exploitation

0.15%

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-444 CWE-444

References

Other References

https://www.ibm.com/support/pages/node/7286610

Frequently Asked Questions

What is CVE-2026-15634? +

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. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-15634? +

CVE-2026-15634 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0025, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-15634? +

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.

Related Vulnerabilities

CVE-2026-116127

Starlet versions before 0.33 for Perl send a body in responses to HEAD requests, corrupting the next response on a …

CVE-2026-73276

Gracefulness code ignored cases that should be rejected, resulting in possible HTTP Request Smuggling opportunities. This issue affects OTP from …

CVE-2026-111750

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, the pure Python parser accepts ambiguous …

CVE-2026-115823

Starman versions before 0.4019 for Perl send response bodies for HEAD requests, desynchronizing responses on keep-alive connections. For a HEAD …

CVE-2026-19203

A client may issue specially crafted HTTP/1.1 chunked requests to a Jetty server that cause Jetty and an intermediary proxy …

CVE-2026-105298

Summary Before version 0.9.0, Pingora accepted HTTP/2 requests whose Host header differed from the :authority pseudo-header. Request filters, cache keys, …