CVE-2026-10725: Protocol::HTTP2 versions through 1.12 for Perl is vulnerable to a HTTP/2 Bomb

[Robert Rothenberg <rrwo () cpansec org>]

=======================================================================
CVE-2026-10725                                       CPAN Security Group
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        CVE ID:  CVE-2026-10725
  Distribution:  Protocol-HTTP2
      Versions:  through 1.12

      MetaCPAN:  https://metacpan.org/dist/Protocol-HTTP2
      VCS Repo:  https://github.com/vlet/p5-Protocol-HTTP2


Protocol::HTTP2 versions through 1.12 for Perl is vulnerable to a
HTTP/2 Bomb

Description
-----------
Protocol::HTTP2 versions through 1.12 for Perl is vulnerable to a
HTTP/2 Bomb.

Protocol::HTTP2's inbound HPACK path has no header-list size limit, so
a small HTTP/2 request can expand into large server memory (the "HTTP/2
bomb").

The headers_decode method materialises a full key+value copy per
indexed reference with no running size check, and the
stream_header_block_add method appends (since version 1.12) every
CONTINUATION frame to the per-stream buffer unbounded.

MAX_HEADER_LIST_SIZE (default 65536) is advertised in SETTINGS but
never consulted on decode.  It is absent from the decoder and from the
:limits export tag.

Problem types
-------------
- CWE-409 Improper Handling of Highly Compressed Data (Data
  Amplification)

Workarounds
-----------
Apply the patch.


References
----------
https://metacpan.org/release/CRUX/Protocol-HTTP2-1.12/source/lib/Protocol/HTTP2/HeaderCompression.pm#L133
https://metacpan.org/release/CRUX/Protocol-HTTP2-1.12/source/lib/Protocol/HTTP2/Stream.pm#L414
https://security.metacpan.org/patches/P/Protocol-HTTP2/1.12/CVE-2026-10725-r1.patch