# CVE-2026-59803: rpcx - Denial of Service via Gzip Decompression Bomb in Wire Protocol

> An unauthenticated attacker can cause a denial of service in rpcx by sending a small gzip-compressed message that expands to consume excessive memory.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 8 Jul 2026
- **Updated:** 9 Jul 2026
- **Also known as:** GHSA-hgrm-22x6-r8c8

## What is CVE-2026-59803?

CVE-2026-59803 is a high-severity denial of service vulnerability in smallnest rpcx, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

rpcx through 1.9.3, fixed in commit 047aec1, contains a denial-of-service vulnerability in protocol.Message.Decode (protocol/message.go). When a message has the compression flag set, the payload is gzip-decompressed via util.Unzip with no limit on the decompressed output size. The only built-in size guard, protocol.MaxMessageLength, is checked against the compressed on-the-wire frame length, not the decompressed size, so it provides no protection. Because decoding (and decompression) occurs in readRequest before authentication, a single unauthenticated connection can send a small (under 2 MB) gzip-compressed message that expands to gigabytes of heap allocation, leading to out-of-memory conditions and service unavailability.

Weakness: CWE-409 (Improper Handling of Highly Compressed Data (Data Amplification))

## Which versions are affected by CVE-2026-59803?


## How do I fix CVE-2026-59803?

No fix has been published for CVE-2026-59803 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-59803 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59803 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59803 and fix it if it is affected.

What it is: CVE-2026-59803 is a high-severity denial of service vulnerability in smallnest rpcx, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59803 exists.

Affected product: smallnest rpcx. 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-2026-59803/ (Markdown: https://insights.sbomify.com/CVE-2026-59803/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59803
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59803
- OSV: https://osv.dev/vulnerability/CVE-2026-59803

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59803/
Summaries are generated and may contain mistakes; the official description above is the record.