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

Published Oct 30, 2026 CVSS 3.1 · 9.1 Critical EPSS < 1% KEV · Not listed
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.

Remediation

Vendor Solution

Upgrade to Starlet 0.33 or later.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H'}

Type Values Removed Values Added
First Time appeared Kazuho
Kazuho starlet
Vendors & Products Kazuho
Kazuho starlet
Type Values Removed Values Added
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.
Title 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
Weaknesses CWE-444
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
CPANSec
Published
Updated
Nov 6, 2026, 4:35 PM
Reserved
Oct 25, 2026, 10:18 AM
Status
Deferred
Published
Oct 30, 2026, 1:18 PM
Modified
Nov 6, 2026, 5:17 PM