elixir-mint up to 1.8.x lib/mint/http2.ex allocation of resources

Summaryinfo

A vulnerability labeled as problematic has been found in elixir-mint mint up to 1.8.x. Affected by this vulnerability is an unknown functionality in the library lib/mint/http2.ex. Executing a manipulation can lead to allocation of resources. This vulnerability is tracked as CVE-2026-48862. The attack can be launched remotely. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in elixir-mint mint up to 1.8.x. It has been declared as problematic. This vulnerability affects an unknown part in the library lib/mint/http2.ex. 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. CVE summarizes:

Allocation of Resources Without Limits or Throttling vulnerability in elixir-mint Mint allows attacker-controlled HTTP/2 servers to exhaust memory in a Mint client via PUSH_PROMISE flooding. In lib/mint/http2.ex, Mint.HTTP2.decode_push_promise_headers_and_add_response/5 inserts a :reserved_remote entry into conn.streams for every promised stream ID. The neighbouring Mint.HTTP2.assert_valid_promised_stream_id/2 only verifies that the promised ID is even and not already present; client_settings.max_concurrent_streams is not consulted at promise time. The concurrency cap is only checked when the response HEADERS for the promised stream arrive, so a server that emits PUSH_PROMISE frames and withholds the matching HEADERS never trips that check. HTTP/2 server push is accepted by default (client_settings.enable_push defaults to true). A single long-lived HTTP/2 connection to a hostile server lets that server pin one conn.streams entry per PUSH_PROMISE frame it sends, with no upper bound, until the client process runs out of memory. This issue affects mint: from 0.2.0 before 1.9.0.

The weakness was disclosed by Peter Ullrich and Jonatan Männchen as GHSA-g586-ccqf-7x4r. The advisory is shared for download at github.com. This vulnerability was named CVE-2026-48862 since 05/25/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 1.9.0 eliminates this vulnerability. Applying the patch 70b97b6a5209fb288b0e04d8e657dda26c59de67 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-33939). Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• elixir-mint

Name

• mint

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8

License

• open-source

Website

• Product: https://github.com/elixir-mint/mint/

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Once again VulDB remains the best source for vulnerability data.

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