CVE-2026-116127: Request Smuggling

Description

Starlet versions before 0.33 for Perl send a body in responses to HEAD requests, corrupting the next response on a persistent or pipelined connection. The request method is not passed to the response writer, so whatever body the application returns for a HEAD request is sent. With Plack::Middleware::Head the body is empty, but an HTTP/1.1 response without a Content-Length header still gets the chunked encoding terminator. Responses with status 204 or 304 are also sent with their body. Pipelined GET and HEAD requests keep the connection open even when keep-alive is disabled, which is the default. A client or proxy reading the connection takes the extra bytes as the start of the next response, which may desynchronize a proxy that shares the connection across clients.

Is your site exposed to CVE-2026-116127?

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

Weakness Type (CWE)

CWE-444 CWE-444

References

Other References

https://github.com/kazuho/Starlet/commit/859e0c9572cdbed4bb45706d3957b3c025dc0ede.patch https://metacpan.org/release/KAZUHO/Starlet-0.33/changes

Frequently Asked Questions

What is CVE-2026-116127? +

Starlet versions before 0.33 for Perl send a body in responses to HEAD requests, corrupting the next response on a persistent or pipelined connection. The request method is not passed to the response writer, so whatever body the application returns for a HEAD request is sent. With Plack::Middleware::Head the body is empty, but an HTTP/1.1 response without a Content-Length header still gets the chunked encoding terminator. Responses with status 204 or 304 are also sent with their body. Pipelined GET and HEAD requests keep the connection open even when keep-alive is disabled, which is the default. A client or proxy reading the connection takes the extra bytes as the start of the next response, which may desynchronize a proxy that shares the connection across clients.

How do I check if I'm vulnerable to CVE-2026-116127? +

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-2025-1867

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in ithewei libhv allows HTTP Response Smuggling.This issue affects libhv: through …

CVE-2024-23316

HTTP request desynchronization in Ping Identity PingAccess, all versions prior to 8.0.1 affected allows an attacker to send specially crafted …

CVE-2024-38494

This vulnerability allows a high-privileged authenticated PAM user to achieve remote command execution on the affected PAM system by sending …

CVE-2025-6999

An HTTP Request Smuggling [CWE-444] vulnerability in the Authentication portal of WatchGuard Fireware OS allows a remote attacker to evade …

CVE-2025-11915

Connection desynchronization between an HTTP proxy and the model backend. The fixes were rolled out for all proxies in front …

CVE-2023-53878

Member Login Script 3.3 contains a client-side desynchronization vulnerability that allows attackers to manipulate HTTP request handling by exploiting Content-Length …

CVE-2026-116127