Vulnerability · Published Jun 1, 2026 · Assigned by VulnCheck

CVE-2026-49140Nanobot < 0.2.1 Denial of Service via Matrix Media Download Handler

Medium 4.3

In plain English

A medium-severity resource allocation without limits in nanobot from HKUDS. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities).

Severity (CVSS 3.1)4.3Medium

Exploit odds (30 days)0.3%top 81.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

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.

Affected products (as reported)

Vendor	Product	Versions
HKUDS	nanobot	0 – before 0.2.1

Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

References

https://github.com/HKUDS/nanobot/releases/tag/v0.2.1 release-notes
https://github.com/HKUDS/nanobot/pull/4106 issue-tracking
https://github.com/HKUDS/nanobot/commit/1d4000560dfff1acb83f5c5ca8ef3ab1f092bd14 patch
https://www.vulncheck.com/advisories/nanobot-denial-of-service-via-matrix-media-download-handler third-party-advisory