CVE-2026-121809: DoS

Description

Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in elixir-grpc grpc_server and grpc allows unauthenticated attackers to occupy a BEAM scheduler indefinitely via a client-streaming or bidirectional-streaming request whose body ends inside a gRPC message. GRPC.Server.Adapters.Cowboy.read_stream/1 (grpc_server/lib/grpc/server/adapters/cowboy.ex, and the Cowboy adapter in grpc before the package split) asks for more data whenever the buffer does not hold a complete message. Once the request body has ended, every further read returns an empty chunk, so the buffer never changes and the function retries without end. A single 5-byte length prefix sent with END_STREAM keeps one scheduler busy for as long as the connection stays open, and repeated requests exhaust all schedulers. This issue affects grpc_server: from 1.0.0 before 1.1.0; grpc: from 0.3.1 before 1.0.0.

Is your site exposed to CVE-2026-121809?

Run a free security scan — no signup, results in seconds.

Weakness Type (CWE)

CWE-400 Uncontrolled Resource Consumption

CWE-835 CWE-835

References

Other References

https://cna.erlef.org/cves/CVE-2026-121809.html https://github.com/elixir-grpc/grpc/commit/0332faae5f5e132314794dbfdae5edecbccea292 https://github.com/elixir-grpc/grpc/commit/38955f1392cbf08eef231a347348445410455c85 https://github.com/elixir-grpc/grpc/commit/6d8a09ad919e208fb600538ac8b19bd733a04310 https://github.com/elixir-grpc/grpc/security/advisories/GHSA-c2h9-f9cc-27xh https://osv.dev/vulnerability/EEF-CVE-2026-121809

Frequently Asked Questions

What is CVE-2026-121809? +

Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in elixir-grpc grpc_server and grpc allows unauthenticated attackers to occupy a BEAM scheduler indefinitely via a client-streaming or bidirectional-streaming request whose body ends inside a gRPC message. GRPC.Server.Adapters.Cowboy.read_stream/1 (grpc_server/lib/grpc/server/adapters/cowboy.ex, and the Cowboy adapter in grpc before the package split) asks for more data whenever the buffer does not hold a complete message. Once the request body has ended, every further read returns an empty chunk, so the buffer never changes and the function retries without end. A single 5-byte length prefix sent with END_STREAM keeps one scheduler busy for as long as the connection stays open, and repeated requests exhaust all schedulers. This issue affects grpc_server: from 1.0.0 before 1.1.0; grpc: from 0.3.1 before 1.0.0.

How do I check if I'm vulnerable to CVE-2026-121809? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-114426

SEPPmail Secure Email Gateway before 15.1.1 processes and writes v1 file-interface upload data before authenticating the caller and without an …

CVE-2026-45802

FPDI is a collection of PHP classes that facilitate reading pages from existing PDF documents and using them as templates …

CVE-2026-67318

axios versions >=1.13.0 (Node.js HTTP adapter) fail to enforce the configured maxBodyLength limit on streamed request bodies when requests are …

CVE-2026-42343

FastGPT is an AI Agent building platform. In versions 4.14.13 and prior, the code-sandbox component suffers from insufficient resource isolation …

CVE-2026-67226

RabbitMQ is a messaging and streaming broker. From 4.0.0 until 4.0.22 and 4.1.14 and 4.2.7, Admin-only atom exhaustion: PUT /api/users …

CVE-2025-41361

Uncontrolled resource consumption vulnerability in IDF v0.10.0-0C03-03 and ZLF v0.10.0-0C03-04. The devices improperly handle TLS requests associated with PROCOME sockets, …

CVE-2026-121809