CVE-2026-17552: Plack::App::Prerender versions before 0.3.0 for Perl can proxy to an arbitrary host via unvalidated REQUEST_URI concatenation in call

[Robert Rothenberg <rrwo () cpansec org>]

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CVE-2026-17552                                       CPAN Security Group
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        CVE ID:  CVE-2026-17552
  Distribution:  Plack-App-Prerender
      Versions:  before 0.3.0

      MetaCPAN:  https://metacpan.org/dist/Plack-App-Prerender
      VCS Repo: https://github.com/robrwo/perl-Plack-App-Prerender


Plack::App::Prerender versions before 0.3.0 for Perl can proxy to an
arbitrary host via unvalidated REQUEST_URI concatenation in call

Description
-----------
Plack::App::Prerender versions before 0.3.0 for Perl can proxy to an
arbitrary host via unvalidated REQUEST_URI concatenation in call.

When the rewrite base is a plain string, the REQUEST_URI is appended to
it, with no check that the path starts with a forward slash ('/').

When the rewrite base does not contain a path (which is the standard
given in the SYNOPSIS), an attacker can create a request that changes
the hostname. A request target starting with an at-sign ('@') changes
the base to a RFC 3986 userinfo component.

For example, a rewrite base of "https://example.com"; with the submitted
request "GET @192.168.1.2/" will send a request to
"https://example.com@192.168.1.2/";, with the rendered content returned
to the attacker.

This allows an attacker to access internal or restricted hosts that
only the webserver has access to.

Problem types
-------------
- CWE-918 Server-Side Request Forgery (SSRF)

Workarounds
-----------
For deployments that cannot be upgraded, change the rewrite to a
function that validates the path before appending it.


Solutions
---------
Upgrade to version 0.3.0 or later.


References
----------
https://github.com/robrwo/perl-Plack-App-Prerender/security/advisories/GHSA-6x4w-x68j-ppqq
https://metacpan.org/release/RRWO/Plack-App-Prerender-v0.3.0/changes
https://github.com/robrwo/perl-Plack-App-Prerender/commit/2d793dd69e2b6f4e469618ee742bd8402677202d.patch