---
id: "CVE-2026-121808"
page: "https://infrastack.ai/live/CVE-2026-121808"
kind: "vulnerability"
aliases: ["CVE-2026-121808"]
title: "elixir-grpc: compressed Erlang terms exhaust server memory without authentication"
severity: "high"
cvss: 8.2
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["elixir", "erlang", "grpc", "package", "self-hosted"]
not_affected_if: ["no-untrusted-grpc-clients", "other-codecs-only"]
published_at: "2026-11-13T16:17:36+00:00"
first_seen_at: "2026-11-13T16:47:33+00:00"
updated_at: "2026-11-13T16:48:31+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121808", "first_seen_at": "2026-11-13T16:47:33+00:00"}]
exploit_sources: []
---

# elixir-grpc: compressed Erlang terms exhaust server memory without authentication

Link for people: https://infrastack.ai/live/CVE-2026-121808 (this .md is for agents)

The Erlpack codec in elixir-grpc decodes message bodies with binary_to_term, which fully inflates a compressed term with no size limit, while the body size limit counts only the compressed bytes. An unauthenticated attacker can send a small request that makes the server allocate far more memory than the request size, exhausting it.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the `grpc` version in `mix.lock` or `mix.exs`; affected if it is from `0.4.0` before `1.0.0`.
- Check the `grpc_core` version in `mix.lock`; affected if it is from `1.0.0` before `1.1.0`.
- Check whether the server accepts `application/grpc+erlpack` requests (the GRPC.Codec.Erlpack codec is in use).

## Fix

- `grpc_core` (1.0.0 to before 1.1.0): upgrade to `1.1.0`.
- `grpc`: fixed version unknown from the sources; the affected range ends at `1.0.0`.

## Timeline

- 2026-11-13T16:47:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121808

## Documents

- [advisory] Vendor advisory: github.com https://github.com/elixir-grpc/grpc/security/advisories/GHSA-xxp9-7hp4-rqwp
- [fix] Patch: github.com https://github.com/elixir-grpc/grpc/commit/0332faae5f5e132314794dbfdae5edecbccea292
- [fix] Patch: github.com https://github.com/elixir-grpc/grpc/commit/25bcc569fe2cc4478531a6c546c923205fc751c9
- [fix] Patch: github.com https://github.com/elixir-grpc/grpc/commit/d6bc56ac75dfb6c02db2099909210a37c9be8db6

## From the sources

Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in elixir-grpc grpc_core and grpc allows unauthenticated attackers to exhaust server memory via a compressed Erlang external term in a gRPC message body.

GRPC.Codec.Erlpack.decode/2 (grpc_core/lib/grpc/codec/erlpack.ex, and lib/grpc/codec/erlpack.ex before the package split) passes the message body to :erlang.binary_to_term/2. That function inflates a compressed term in full before it returns. The codec sets no limit on the decoded size, and its type checks run only on the decoded term. The server's max_body_size limit counts the compressed bytes of the request. A request with Content-Type: application/grpc+erlpack can therefore make the server allocate a term much larger than the request body.

This issue affects grpc: from 0.4.0 before 1.0.0; grpc_core: from 1.0.0 before 1.1.0.

---

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