CVE
Memory exhaustion in Erlpack codec
Only affects grpc from 0.4.0 before 1.0.0 and grpc_core from 1.0.0 before 1.1.0, when GRPC.Codec.Erlpack is registered as a codec on the gRPC server. Fixed in grpc 1.0.0 and grpc_core 1.1.0.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in grpc 1.0.0 · grpc_core 1.1.0
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. Affected grpc versions: from 0.4.0 before 1.0.0, or grpc_core from 1.0.0 before 1.1.0. GRPC.Codec.Erlpack is registered as a codec on the gRPC server.
- Published
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- 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? →
- 30/100 · 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? →
- Specific setups only
- 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
Unauthenticated attackers can remotely exhaust server memory in the elixir-grpc grpc and grpc_core packages by sending a gRPC request with a compressed Erlang term in the Erlpack format. The codec fully expands the term before any size check applies, so a small request can force the server to allocate far more memory than the request body contains.
Read the original 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.
Who should check
Teams running elixir-grpc grpc from 0.4.0 before 1.0.0, or grpc_core from 1.0.0 before 1.1.0, that register GRPC.Codec.Erlpack on a gRPC server.
Read the source excerpt
“This issue affects grpc: from 0.4.0 before 1.0.0; grpc_core: from 1.0.0 before 1.1.0.”
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure12/25Specific setups only, reachable over the network without a login
- 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
What to do
Check whether your setup matches what the bug needs.
Affected grpc versions: from 0.4.0 before 1.0.0, or grpc_core from 1.0.0 before 1.1.0. GRPC.Codec.Erlpack is registered as a codec on the gRPC server.Upgrade to a fixed version: grpc 1.0.0 · grpc_core 1.1.0.
Workaround: Remove GRPC.Codec.Erlpack from the server's codecs list if the codec is not needed.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-121808 (Memory exhaustion via compressed Erlang terms in the elixir-grpc Erlpack codec), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-121808 (entry last updated 2026-11-13):
Affected:
- Hex package grpc: from 0.4.0, fixed in 1.0.0
- elixir-grpc grpc: version range not reported
- Hex package grpc_core: from 1.0.0, fixed in 1.1.0
- elixir-grpc grpc_core: version range not reported
- Hex package grpc: from 0.4.0, fixed in 1.0.0
- Hex package grpc_core: from 1.0.0, fixed in 1.1.0
Fixed versions: 1.0.0, 1.1.0.
Conditions (all must be true for the bug to be hit):
- Affected grpc versions: from 0.4.0 before 1.0.0, or grpc_core from 1.0.0 before 1.1.0. (source: https://cna.erlef.org/cves/CVE-2026-121808.html)
- GRPC.Codec.Erlpack is registered as a codec on the gRPC server. (source: https://github.com/elixir-grpc/grpc/security/advisories/GHSA-xxp9-7hp4-rqwp)
Setup: the bug needs a feature or setting that is off by default or uncommon. Check whether each asset has it on.
Attacker needs: network access, no login, no user action.
Workaround: Remove GRPC.Codec.Erlpack from the server's codecs list if the codec is not needed. (source: https://cna.erlef.org/cves/CVE-2026-121808.html)
CISA KEV: CVE-2026-121808 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-121808 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Packages (Hex): find every lockfile in each project and run the stack.check operation of the cve.now MCP server (execute) on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/elixir-grpc/grpc/security/advisories/GHSA-xxp9-7hp4-rqwp
- https://github.com/elixir-grpc/grpc/commit/0332faae5f5e132314794dbfdae5edecbccea292
- https://github.com/elixir-grpc/grpc/commit/d6bc56ac75dfb6c02db2099909210a37c9be8db6
- https://cna.erlef.org/cves/CVE-2026-121808.html
- https://osv.dev/vulnerability/EEF-CVE-2026-121808
- https://github.com/elixir-grpc/grpc/commit/25bcc569fe2cc4478531a6c546c923205fc751c9
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-121808
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-121808"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
Evidence 8
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-121808
Is CVE-2026-121808 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?
A compressed Erlang external term sent in a gRPC message body can be expanded by the server far beyond the size of the request, which can exhaust server memory. The advisory says this can be triggered by an unauthenticated request.Source: cna.erlef.org, github.com
Which versions are affected by CVE-2026-121808?
grpc (Hex): from 0.4.0 before 1.0.0. grpc_core (Hex): from 1.0.0 before 1.1.0. grpc (Hex): from 0.4.0 before 1.0.0. grpc_core (Hex): from 1.0.0 before 1.1.0.Source: cve.now feed data
Am I affected, and how do I check?
Affected versions are grpc from 0.4.0 before 1.0.0 and grpc_core from 1.0.0 before 1.1.0. The setup matters: GRPC.Codec.Erlpack must be explicitly registered as a codec on the gRPC server. To check, look at the grpc or grpc_core version in the project's dependency lock file and at the server's codecs list for GRPC.Codec.Erlpack.Source: cna.erlef.org, github.com
How do I fix CVE-2026-121808?
Upgrade grpc to 1.0.0 or later, or grpc_core to 1.1.0 or later. If the Erlpack codec is not needed, remove GRPC.Codec.Erlpack from the server's codecs list.Source: cna.erlef.org, github.com