# CVE-2026-48521: Null dereference in envoy

> Attackers can crash Envoy workers via null pointer dereference in HTTP/3 connection pool selection when specific contexts lack transport socket options.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Sep 2026
- **Updated:** 21 Sep 2026
- **Also known as:** BIT-envoy-2026-48521, GHSA-5vff-j9p4-38j3, MINI-94hj-wv67-x4r3, MINI-c63p-48mq-h5h6, MINI-pgwv-hm33-2gxm, MINI-r2ff-h3c7-c892

## What is CVE-2026-48521?

CVE-2026-48521 is a medium-severity vulnerability in Envoyproxy Envoy, published on 21 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy's ProdClusterManagerFactory::allocateConnPool dereferences transport_socket_options while selecting an HTTP/3 connection pool without first checking whether the pointer is null. LoadBalancerContext implementations used by synthetic, mirror, health-check, and async-client calls can return no transport-socket options. With auto_config and HTTP/3 enabled, routine traffic reaching one of those contexts can crash an Envoy worker. The relevant scope boundary is that the affected branch requires HTTP/3 in the protocol set and a context that supplies no transport-socket options. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-48521?

1 open source package ship an affected version, including envoy. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `envoy` | Bitnami | All versions | 1.36.10, 1.37.6, 1.38.4, 1.39.1 |

Products: Envoyproxy Envoy.

## How do I fix CVE-2026-48521?

Upgrade envoy to a fixed version for your release line: 1.36.10, 1.37.6, 1.38.4 or 1.39.1.

## Is CVE-2026-48521 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48521 exists.

## Other vulnerabilities in Envoyproxy Envoy

- [CVE-2022-29226](https://insights.sbomify.com/CVE-2022-29226/): Trivial authentication bypass in Envoy (critical 10.0)
- [CVE-2019-18801](https://insights.sbomify.com/CVE-2019-18801/): Memory corruption in n/a (critical 9.8)
- [CVE-2019-18802](https://insights.sbomify.com/CVE-2019-18802/): Security feature bypass in n/a (critical 9.8)
- [CVE-2020-35470](https://insights.sbomify.com/CVE-2020-35470/): Information disclosure in n/a (high 8.8)
- [CVE-2024-23324](https://insights.sbomify.com/CVE-2024-23324/): Envoy ext auth can be bypassed when Proxy protocol filter sets invalid UTF-8 metadata (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48521 and fix it if it is affected.

What it is: CVE-2026-48521 is a medium-severity vulnerability in Envoyproxy Envoy, published on 21 Sep 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-2026-48521 exists.

Affected packages and fixed versions:
- envoy (Bitnami): affected all versions; fixed in 1.36.10, 1.37.6, 1.38.4, 1.39.1

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-2026-48521/ (Markdown: https://insights.sbomify.com/CVE-2026-48521/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48521
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48521
- OSV: https://osv.dev/vulnerability/CVE-2026-48521

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48521/
Summaries are generated and may contain mistakes; the official description above is the record.