# CVE-2026-54451: Elixir Protobuf uncontrolled recursion in decoder

Source: https://junglewise.ai/threats/cve-2026-54451-elixir-protobuf-uncontrolled-recursion-in-decoder  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-17. Updated: 2026-07-15  
License: CC BY 4.0 with a link back

CVE-2026-54451 · Severity: high · CVSS 8.2 · Published 2026-09-17

A vulnerability in the Elixir Protobuf library allows an unauthenticated attacker to crash services that process specially crafted data. By sending a small but deeply nested message, an attacker can exhaust a server's memory and processing power, leading to a total service outage. This affects any application using this library to decode data formats that allow self-referencing structures, such as comment threads or file trees.

## Quick answers

**Is CVE-2026-54451 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-54451 being exploited in the wild.

**How severe is CVE-2026-54451?** High severity, with a CVSS score of 8.2, published 17 September 2026.

**Which products and versions are affected?** elixir-protobuf protobuf >= 0.8.0, < 0.16.1.

**Is there a fix for CVE-2026-54451?** A patch was published on 2026-07-15: Fix released in version 0.16.1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-54451 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-54451?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in the `Protobuf.Decoder.value_for_field/3` function of the Elixir `protobuf` package. When decoding embedded message fields, the decoder performs recursive calls that are not in tail position, causing each nesting level to retain a live frame on the process stack and heap. Because there is no recursion-depth limit, an attacker can provide a payload with hundreds of thousands of nesting levels using a self-referential or cyclic message schema. This results in a request-amplification denial of service (DoS) by exhausting memory or starving the BEAM scheduler. The issue is resolved in version 0.16.1 by introducing a configurable recursion limit (defaulting to 100).

## Affected products

- elixir-protobuf protobuf >= 0.8.0, < 0.16.1

## Identifiers

- CVE-2026-54451
- GHSA-rv48-qqj5-crxg

## Timeline

- 2026-06-04: disclosed: Initial disclosure to the maintainers
- 2026-07-15: advisory: GitHub Advisory published
- 2026-07-15: patched: Fix released in version 0.16.1

## References

- [https://api.github.com/users/PJUllrich](https://api.github.com/users/PJUllrich)
- [https://github.com/PJUllrich](https://github.com/PJUllrich)
- [https://api.github.com/users/PJUllrich/gists%7B/gist_id%7D](https://api.github.com/users/PJUllrich/gists%7B/gist_id%7D)
- [https://api.github.com/users/PJUllrich/repos](https://api.github.com/users/PJUllrich/repos)
- [https://avatars.githubusercontent.com/u/10426523?v=4](https://avatars.githubusercontent.com/u/10426523?v=4)
- [https://api.github.com/users/PJUllrich/events%7B/privacy%7D](https://api.github.com/users/PJUllrich/events%7B/privacy%7D)