grpc: Improper Handling of Highly Compressed Data (Data Amplification)
CVE-2026-121808 is a high-severity improper handling of highly compressed data (data amplification) vulnerability in grpc from Elixir-grpc, with a CVSS 4.0 base score of 8.2 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 1.0.0, 0332faae5f5e132314794dbfdae5edecbccea292 as the first without the flaw, so updating grpc to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.7% chance of exploitation within 30 days, higher than 54% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update grpc to 1.0.0 or 0332faae5f5e132314794dbfdae5edecbccea292, whichever matches your release line, or a later version.
- Update grpc_core to 1.1.0 or d6bc56ac75dfb6c02db2099909210a37c9be8db6, whichever matches your release line, or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Elixir-grpc | grpc | 0.4.0 up to, but not including, 1.0.0; 25bcc569fe2cc4478531a6c546c923205fc751c9 up to, but not including, 0332faae5f5e132314794dbfdae5edecbccea292 | 1.0.0, 0332faae5f5e132314794dbfdae5edecbccea292 |
| Elixir-grpc | grpc_core | 1.0.0 up to, but not including, 1.1.0; 0332faae5f5e132314794dbfdae5edecbccea292 up to, but not including, d6bc56ac75dfb6c02db2099909210a37c9be8db6 | 1.1.0, d6bc56ac75dfb6c02db2099909210a37c9be8db6 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Attack requirements
- PresentThe target must be in a specific state or configuration for the attack to work.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Confidentiality (vulnerable system)
- NoneNo loss of confidentiality on the vulnerable system.
- Integrity (vulnerable system)
- NoneNo loss of integrity on the vulnerable system.
- Availability (vulnerable system)
- HighSerious loss of availability on the vulnerable system.
- Confidentiality (other systems)
- NoneNo loss of confidentiality on systems beyond the vulnerable one.
- Integrity (other systems)
- NoneNo loss of integrity on systems beyond the vulnerable one.
- Availability (other systems)
- NoneNo loss of availability on systems beyond the vulnerable one.
Vector: 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. Scored by CNA.
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Handling of Highly Compressed Data (Data Amplification)
The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.
More Improper Handling of Highly Compressed Data (Data Amplification) vulnerabilities (CWE-409)
Timeline
- CVE record published.
References
Patches and release notes
Other vulnerabilities in grpc
- 8.2 High severity
- 7.6 High severity
- 8.7 High severity
- 8.7 High severity
- 9.2 Critical severity
- 7.6 High severity
Recent Improper Handling of Highly Compressed Data (Data Amplification) vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 8.2 High severity
- 8.7 High severity
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