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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-85534?
How do I fix CVE-2026-85534?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-85534 being exploited?
There is no known exploitation of CVE-2026-85534 in the wild and no public exploit code.
Sources
Also known as AZL-99912, DEBIAN-CVE-2026-85534, ECHO-66c6-ea78-4d6c, GHSA-qm5f-xr9c-mm27, UBUNTU-CVE-2026-85534.