CVE-2026-121808

Description

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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Weakness Type (CWE)

CWE-409 CWE-409

References

Other References

https://cna.erlef.org/cves/CVE-2026-121808.html https://github.com/elixir-grpc/grpc/commit/0332faae5f5e132314794dbfdae5edecbccea292 https://github.com/elixir-grpc/grpc/commit/25bcc569fe2cc4478531a6c546c923205fc751c9 https://github.com/elixir-grpc/grpc/commit/d6bc56ac75dfb6c02db2099909210a37c9be8db6 https://github.com/elixir-grpc/grpc/security/advisories/GHSA-xxp9-7hp4-rqwp https://osv.dev/vulnerability/EEF-CVE-2026-121808

Frequently Asked Questions

What is CVE-2026-121808? +

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.

How do I check if I'm vulnerable to CVE-2026-121808? +

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.

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