# CVE-2026-71397: Unbounded request body accumulation on streaming RPCs causes memory exhaustion in grpc_server

Status: published. Published: 2026-11-06. Updated: 2026-11-06.

Allocation of Resources Without Limits or Throttling vulnerability in elixir-grpc grpc_server allows unauthenticated attackers to exhaust memory and crash the node via an oversized client-streaming or bidirectional-streaming request body.

The streaming read clause of 'Elixir.GRPC.Server.Adapters.Cowboy.Handler':info/3 (grpc_server/lib/grpc/server/adapters/cowboy/handler.ex) never checks the configured max_body_size. Only the unary read path enforces that cap. 'Elixir.GRPC.Server.Adapters.Cowboy':reading_stream/1 (grpc_server/lib/grpc/server/adapters/cowboy.ex) appends every received chunk to its buffer until a complete length-prefixed message arrives. A client can declare a very large message and send it across many small HTTP/2 DATA frames, and the server buffers all of it.

This issue affects grpc_server: from 1.0.0 before 1.0.6.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/elixir-grpc/grpc/commit/0b663ca53dbf0f36f7f67ff1d0026f4482a18915

## Affected products and versions

- elixir-grpc / grpc_server (grpc_server): ≥ 1.0.0; < 1.0.6 (affected, semver). Source: CNA: EEF
- elixir-grpc / grpc_server (elixir-grpc/grpc): ≥ 49e18c3ec6bb9afe2f712caad3dbab5c56a68a00; < 0b663ca53dbf0f36f7f67ff1d0026f4482a18915 (affected, git). Source: CNA: EEF

## Severity and prioritization

- CVSS 4.0: 8.2 (high); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: EEF

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-770

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/elixir-grpc/grpc/security/advisories/GHSA-vx6q-cr5q-945g (CNA: EEF; vendor-advisory, related)

- https://cna.erlef.org/cves/CVE-2026-71397.html (CNA: EEF; related)

- https://osv.dev/vulnerability/EEF-CVE-2026-71397 (CNA: EEF; related)

- https://github.com/elixir-grpc/grpc/commit/49e18c3ec6bb9afe2f712caad3dbab5c56a68a00 (CNA: EEF; related)

- https://github.com/elixir-grpc/grpc/commit/0b663ca53dbf0f36f7f67ff1d0026f4482a18915 (CNA: EEF; patch)

## Provenance

- CNA: EEF: https://www.cve.org/CVERecord?id=CVE-2026-71397; retrieved 2026-11-06; source updated 2026-11-06

Revision: c94c67584bd6673a13611e924f4a3180999bf982f9e9b52123751875088a9619

Canonical: https://y2.dev/cve/CVE-2026-71397

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