Vulnerabilities

Vulnerability · CVE-2026-104635

Uncontrolled Recursion

Published Oct 9, 2026 · catalog updated Oct 15, 2026 · Uncontrolled Recursion

Check if you run it

No confirmed exploitation is on record for CVE-2026-104635. EPSS is 0.39%. Act only if a listed version of Uncontrolled Recursion is installed.

Severity

High8.2

Known exploitation

Not in CISA/VulnCheck KEV

EPSS

0.39%

Remediation

Advisory link

Affected products

Hex protobuf · hex protobuf

## Summary Uncontrolled Recursion vulnerability in in elixir-protobuf protobuf allows an unauthenticated remote attacker to crash the decoding process via a deeply nested JSON document. Any application that decodes attacker-supplied JSON with , , or into a schema that contains a self-referential or cyclic message type is affected. In , the embedded-message clause of recurses into once per nesting level without incrementing or checking the decoder's depth counter. The depth guard covers only the and clauses, so the option has no effect on user-defined message types. Each nesting level allocates a stack frame and heap objects, and a sufficiently deep document exhausts the memory of the decoding process. Confidentiality and integrity are not affected. This issue affects protobuf: from 0.8.0 before 0.17.1. ## Details **1. Entry points.** , , and in validate options and call , which builds a map carrying and the (default 100). accepts already-parsed data, so the underlying JSON parser never bounds the depth either. **2. Unguarded recursion.** For a user-defined message module, calls , which calls and . Each field value passes through and, for a singular embedded message, reaches the clause matching . That clause calls with unchanged, so stays at 0 at every nesting level. Repeated fields and map values reach the same clause through and . **3. Guard coverage.** increments and throws when it exceeds the limit. It is called only from the and clauses, which the clause delegates to. The documentation scopes the option to those wrappers, and no other path checks depth. **4. Result.** A self-referential schema such as a message with a field recurses once per JSON nesting level with no bound. Each level holds a live stack frame and allocates heap objects, so a sufficiently deep document exhausts the memory of the decoding process and crashes it. The BEAM process flag defaults to unlimited, so repeated or concurrent requests can exhaust the memory of the whole node. ## Proof of co