ninenines cowlib 2.0.0/2.18.0 HPACK/QPACK prefixed-integer decoder src/cow_hpack_common.hrl cow_hpack_common:dec_big_int/3 allocation of resources

Summaryinfo

A vulnerability has been found in ninenines cowlib 2.0.0/2.18.0 and classified as problematic. This issue affects the function cow_hpack_common:dec_big_int/3 of the file src/cow_hpack_common.hrl of the component HPACK/QPACK prefixed-integer decoder. This manipulation causes allocation of resources. This vulnerability is tracked as CVE-2026-59248. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability has been found in ninenines cowlib 2.0.0/2.18.0 and classified as problematic. Affected by this vulnerability is the function cow_hpack_common:dec_big_int/3 of the file src/cow_hpack_common.hrl of the component HPACK/QPACK prefixed-integer decoder. The manipulation with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. As an impact it is known to affect availability. The summary by CVE is:

Allocation of resources without limits vulnerability in ninenines cowlib allows an unauthenticated remote HTTP/2 or HTTP/3 peer to exhaust memory on the vulnerable server (or client) and cause a denial of service. The HPACK and QPACK prefixed-integer decoder cow_hpack_common:dec_big_int/3 in src/cow_hpack_common.hrl (invoked from cow_hpack:decode/2 in src/cow_hpack.erl and from cow_qpack:decode_field_section/3 in src/cow_qpack.erl) reads continuation octets until it sees one whose high bit is clear, evaluating Int + (Value bsl M) at each step with the shift M growing by seven per octet. No limit is enforced on the number of continuation octets, on the resulting bit width, or on the value; the decoder consumes whatever encoded length the peer supplies. Because Erlang integers are immutable, each intermediate Value bsl M and each accumulator update allocates a fresh bignum whose digit width grows linearly with the number of octets processed so far. Summed across the whole decode, the transient bignum digit materialization is on the order of the square of the encoded length. A single maximal HPACK indexed representation carried inside one HTTP/2 HEADERS plus one CONTINUATION frame at Cowboy's default max_frame_size_received can force hundreds of megabytes of transient allocation and garbage-collection churn before the resulting header-table index is rejected as invalid. Repeated or concurrent connections multiply the pressure and can drive the Erlang VM to memory exhaustion. Cowlib is the HTTP parser used by Cowboy, RabbitMQ's management plugin, and other Erlang and Elixir HTTP/2 and HTTP/3 servers and clients, so any exposed endpoint that accepts HPACK or QPACK from an untrusted peer is reachable. This issue affects cowlib: from 2.0.0 before 2.19.0.

It is possible to read the advisory at cna.erlef.org. This vulnerability is known as CVE-2026-59248 since 07/04/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 2.19.0 eliminates this vulnerability.

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Productinfo

Vendor

• ninenines

Name

• cowlib

Version

• 2.0.0
• 2.18.0

CPE 2.3info

• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒

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