# CVE-2026-78066: Apache bRPC: Resource Exhaustion via Unbounded Decompression and Unvalidated Wire-Declared Sizes


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 21 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** GHSA-qvxp-6v5r-47h4

## What is CVE-2026-78066?

CVE-2026-78066 is a vulnerability in Apache bRPC, published on 21 Oct 2026. 

### Official description

Resource exhaustion in Apache bRPC (version < 1.18.0) on all platforms: multiple parsers that accept wire-controlled input bound no limit on the sizes declared by the client or on decompressed output, which attackers can use to drive disproportionate memory use and crash the process.

Root Cause:
1) The gzip/zlib/snappy decompressors enforce no output limit: -max_body_size is checked against the compressed bytes only, so a cap-compliant body (e.g. 64 MiB) can decompress to tens of GiB.
2) The AMF string readers allocate the declared length before the bytes are actually available.
3) RTMP chunk headers may re-declare a message length mid-stream; the declared length was never bounded and the partial reassembly buffer kept growing.
4) The sofa-pbrpc parser does not bound meta_size.
5) mcpack2pb trusts wire-declared item counts for Reserve() and a string value_size of 0 underflows the buffer size, aborting the process.

Affected Scenarios:
Any bRPC service accepting gzip/zlib/snappy-compressed bodies or rtmp, sofa-pbrpc, or mcpack2pb messages from untrusted clients.

How to Fix:(Choose one of the following options) 1. Upgrade bRPC to version 1.18.0, which fixes this issue.

2. Apply this patch: https://github.com/apache/brpc/pull/3476

Note:
After the fix, requests whose decompressed size, RTMP message length, or mcpack declared count exceed the new limits are rejected. Operators who legitimately need larger values can raise the corresponding flag (-max_decompressed_body_size, max_body_size).

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-78066?


## How do I fix CVE-2026-78066?

No fix has been published for CVE-2026-78066 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-78066 being exploited?

There is no known exploitation of CVE-2026-78066 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-78066 and fix it if it is affected.

What it is: CVE-2026-78066 is a vulnerability in Apache bRPC, published on 21 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-78066 in the wild and no public exploit code.

Affected product: Apache bRPC. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-78066/ (Markdown: https://insights.sbomify.com/CVE-2026-78066/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-78066
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-78066
- OSV: https://osv.dev/vulnerability/CVE-2026-78066

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-78066/
Summaries are generated and may contain mistakes; the official description above is the record.