# CVE-2026-9678: undici vulnerable to cross-user information disclosure via shared cache whitespace bypass

> Attackers can read other users' authenticated data via shared cache when whitespace-padded cache headers bypass security checks in undici.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Jun 2026
- **Updated:** 17 Jun 2026
- **Also known as:** DEBIAN-CVE-2026-9678, ECHO-8994-d1aa-91ab, GHSA-pr7r-676h-xcf6, MINI-37m7-pqxf-864q, MINI-49jg-32vr-h3xx, MINI-4qj9-vj73-vfwv, MINI-889v-6gfm-7m7f, MINI-9v53-87mm-5558, MINI-h6g2-vvqj-f842, MINI-jq4w-j69r-85c3, MINI-qjf7-6v96-prcg, MINI-xq7w-v4r8-wp6r, ROOT-APP-NPM-CVE-2026-9678, UBUNTU-CVE-2026-9678

## What is CVE-2026-9678?

CVE-2026-9678 is a medium-severity vulnerability in Nodejs Undici, published on 17 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Impact:
Undici's cache interceptor incorrectly classifies some responses as cacheable when the upstream Cache-Control header uses whitespace-padded qualified private or no-cache field names such as private=" authorization" or no-cache="\tauthorization". The parser preserves the surrounding whitespace, so later comparisons against the literal authorization field name fail and the response is stored.

In shared-cache mode, this allows a response containing one user's authenticated data to be served from cache to a subsequent caller, including an unauthenticated caller, when both requests resolve to the same cache key.

Affected applications are those that explicitly enable the cache interceptor (interceptors.cache()) in shared mode, forward Authorization headers upstream, and receive cacheable responses with non-canonical qualified private or no-cache directives.

Patches:
Upgrade to undici v7.28.0 or v8.5.0.

Workarounds:
If upgrade is not immediately possible, disable shared-cache mode for traffic that includes Authorization headers, avoid caching responses to authenticated requests, or add Vary: Authorization upstream.

Weakness: CWE-524 (Use of Cache Containing Sensitive Information)

## Which versions are affected by CVE-2026-9678?

4 open source packages ship an affected version, including undici. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `undici` | npm | From 7.0.0 | 7.28.0 |
| `undici` | npm | From 7.0.0 | 7.28.0 |
| `undici` | npm | From 8.0.0 | 8.5.0 |
| `undici` | npm | From 8.0.0 | 8.5.0 |

Products: Nodejs Undici.

## How do I fix CVE-2026-9678?

Upgrade undici to a fixed version for your release line: 7.28.0 or 8.5.0.

## Is CVE-2026-9678 being exploited?

There is no known exploitation of CVE-2026-9678 in the wild and no public exploit code.

## Other vulnerabilities in Nodejs Undici

- [CVE-2026-109855](https://insights.sbomify.com/CVE-2026-109855/): undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake (high 7.5)
- [CVE-2026-109869](https://insights.sbomify.com/CVE-2026-109869/): undici vulnerable to Denial of Service via unhandled error on excessive content-encodings (high 7.5)
- [CVE-2026-87018](https://insights.sbomify.com/CVE-2026-87018/): undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation (high 7.5)
- [CVE-2026-19534](https://insights.sbomify.com/CVE-2026-19534/): undici vulnerable to Denial of Service via unrequested WebSocket subprotocol (high 7.5)
- [CVE-2026-12151](https://insights.sbomify.com/CVE-2026-12151/): undici WebSocket client vulnerable to denial of service via fragment count bypass (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-9678 and fix it if it is affected.

What it is: CVE-2026-9678 is a medium-severity vulnerability in Nodejs Undici, published on 17 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-9678 in the wild and no public exploit code.

Affected packages and fixed versions:
- undici (npm): affected from 7.0.0; fixed in 7.28.0
- undici (npm): affected from 7.0.0; fixed in 7.28.0
- undici (npm): affected from 8.0.0; fixed in 8.5.0
- undici (npm): affected from 8.0.0; fixed in 8.5.0

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-2026-9678/ (Markdown: https://insights.sbomify.com/CVE-2026-9678/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-9678
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-9678
- OSV: https://osv.dev/vulnerability/CVE-2026-9678

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-9678/
Summaries are generated and may contain mistakes; the official description above is the record.