Unbounded request body accumulation on streaming RPCs causes memory exhaustion in grpc_server
Affects grpc_server from 1.0.0 before 1.0.6 on servers that expose at least one client-streaming or bidirectional-streaming RPC method. Fixed in 1.0.6.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 1.0.6
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 1.0.6.
- Last modified
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 35/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Unclear
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
The elixir-grpc grpc_server library is affected by a flaw where its streaming RPC handling buffers an entire oversized client request body without enforcing the configured size limit. A remote, unauthenticated attacker can exhaust server memory and crash the node by sending a very large message split across many small HTTP/2 frames.
Read the original description
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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed, reachable over the network without a login · Unknown: Advisories don't say whether default setups are affected
- Reach10/20Affects Hex packages
- Severity8.2/10CVSS 8.2
- No patch0/5No signal
What would change the score
- Would score about 80 if added to CISA KEV
- Would score about 75 if CISA's SSVC rates exploitation active
- Would score about 40 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 1.0.6.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- grpc_serverHex
From 1.0.0 · fixed in 1.0.6
- elixir-grpc/grpc
Version range not reported
- grpc_serverHex
From 1.0.0 · fixed in 1.0.6
Evidence 5
- Advisory
- Patch
- Repository
- Link
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-71397
Is CVE-2026-71397 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
An unauthenticated client can exhaust a grpc_server node's memory through a single streaming RPC connection, crashing the node and taking down every service on it.Source: cve.org, cna.erlef.org
Which versions are affected by CVE-2026-71397?
grpc_server (Hex): from 1.0.0 before 1.0.6. grpc_server (Hex): from 1.0.0 before 1.0.6.Source: cve.now feed data
Am I affected, and how do I check?
Versions from 1.0.0 before 1.0.6 are affected, but only on servers that expose at least one client-streaming or bidirectional-streaming RPC method. To check, look at the grpc_server version in the project's dependency lock file and review the service definitions for streaming RPC methods.Source: cve.org, cna.erlef.org
How do I fix CVE-2026-71397?
Upgrade grpc_server to 1.0.6 or later, which contains the fix. The sources provided do not list a workaround.Source: cve.org, cna.erlef.org