What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-01 · updated 2026-07-22
• Weakness: CWE-770

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

• HKUDS nanobot: before 0.2.1 — fixed in 0.2.1

How to fix

Upgrade to a fixed version: HKUDS nanobot 0.2.1. Check the vendor advisory for mitigations.

References

• https://github.com/HKUDS/nanobot/commit/1d4000560dfff1acb83f5c5ca8ef3ab1f092bd14
• https://github.com/HKUDS/nanobot/pull/4106
• https://github.com/HKUDS/nanobot/releases/tag/v0.2.1
• https://www.vulncheck.com/advisories/nanobot-denial-of-service-via-matrix-media-download-handler
• https://github.com/HKUDS/nanobot/pull/4106

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