elixir-lang Elixir URI lib/elixir/lib/uri.ex URI.parse resource consumption

Summaryinfo

A vulnerability, which was classified as problematic, has been found in elixir-lang Elixir. This affects the function URI.parse of the file lib/elixir/lib/uri.ex of the component URI. The manipulation leads to resource consumption. This vulnerability is referenced as CVE-2026-109821. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in elixir-lang Elixir (affected version unknown). It has been rated as problematic. This issue affects the function URI.parse of the file lib/elixir/lib/uri.ex of the component URI. The manipulation with an unknown input leads to a resource consumption vulnerability. Using CWE to declare the problem leads to CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. Impacted is availability. The summary by CVE is:

Improper Validation of Specified Quantity in Input vulnerability in the Elixir standard library's URI module allows an attacker who supplies a URL to cause a denial of service through CPU exhaustion. URI.parse/1 converts the port component with String.to_integer/1 in split_authority/1 (lib/elixir/lib/uri.ex) without bounding its length, so a port of up to 1,262,592 decimal digits produces a bignum of that size and a longer one raises SystemLimitError. Rendering the parsed URI back to text (URI.to_string/1, inspect/1, logging, error formatting) converts the bignum with :erlang.integer_to_binary/1, which is quadratic on Erlang/OTP 27, 28 and 29.0: a 400,000-digit port renders in about 2.6 seconds and a 1 MB port in about 18 seconds. Ports above 65535 are also accepted. This issue affects elixir: from 0.5.0 before 1.18.6, from 1.19.0-rc.0 before 1.19.7, and from 1.20.0-rc.0 before 1.20.5.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-109821 since 10/23/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. 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.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• elixir-lang

Name

• Elixir

Website

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

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