CVE-2026-49140 Nanobot < 0.2.1 Denial of Service via Matrix Media Download Handler
Authenticated users can cause denial of service in Nanobot by sending Matrix media events with invalid size metadata, exhausting memory and bandwidth.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-49140?
CVE-2026-49140 is a medium-severity denial of service vulnerability in HKUDS nanobot, published on 1 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Nanobot prior to version 0.2.1 contains a denial of service vulnerability in the Matrix channel media download handler that allows authenticated room members to exhaust process memory and bandwidth by sending media events with missing or invalid size metadata. Attackers can send multiple concurrent Matrix media events with omitted or invalid declared sizes to trigger simultaneous large media downloads that fully materialize response bodies before post-download rejection, consuming process resources until service degradation occurs.
Weakness: CWE-770
Which versions are affected by CVE-2026-49140?
How do I fix CVE-2026-49140?
No fix has been published for CVE-2026-49140 yet. Limit exposure of the affected software until one is available.
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-2026-49140 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-49140 exists.
Sources
Also known as GHSA-4rm2-fq3x-g7x7.