# CVE-2026-85534: Denial of service in Red Hat Enterprise Linux 10

> A malicious HTTP/2 server can crash the libsoup client by shrinking the flow-control window during a deferred body read, causing a process abort.

- **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:** 4 Sep 2026
- **Updated:** 4 Sep 2026
- **Also known as:** AZL-99912, DEBIAN-CVE-2026-85534, ECHO-66c6-ea78-4d6c, GHSA-qm5f-xr9c-mm27, UBUNTU-CVE-2026-85534

## What is CVE-2026-85534?

CVE-2026-85534 is a medium-severity denial of service vulnerability in Red Hat Enterprise Linux 10, published on 4 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in libsoup. When a client sends an HTTP/2 request body from a non-pollable input stream, the library can buffer more data than the current flow-control window later allows. A malicious HTTP/2 server can shrink SETTINGS_INITIAL_WINDOW_SIZE while that buffered read is still in progress. The client then copies the full buffer into a smaller DATA callback without a runtime bounds check, which can abort the process or fail the HTTP/2 session.

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2026-85534?


## How do I fix CVE-2026-85534?

Apply the vendor's patch.

## Is CVE-2026-85534 being exploited?

There is no known exploitation of CVE-2026-85534 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-85534 and fix it if it is affected.

What it is: CVE-2026-85534 is a medium-severity denial of service vulnerability in Red Hat Enterprise Linux 10, published on 4 Sep 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-2026-85534 in the wild and no public exploit code.

Affected product: Red Hat Enterprise Linux 10. 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-2026-85534/ (Markdown: https://insights.sbomify.com/CVE-2026-85534/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-85534
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-85534
- OSV: https://osv.dev/vulnerability/CVE-2026-85534

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-85534/
Summaries are generated and may contain mistakes; the official description above is the record.