Low severity · published Feb 3, 2026
CVE-2026-25224
Fastify Vulnerable to DoS via Unbounded Memory Allocation in sendWebStream
3.7
CVSS
0.6%
EPSS
No
On KEV
Description
Fastify is a fast and low overhead web framework, for Node.js. Prior to version 5.7.3, a denial-of-service vulnerability in Fastify’s Web Streams response handling can allow a remote client to exhaust server memory. Applications that return a ReadableStream (or Response with a Web Stream body) via reply.send() are impacted. A slow or non-reading client can trigger unbounded buffering when backpressure is ignored, leading to process crashes or severe degradation. This issue has been patched in version 5.7.3.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 46% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FA
fastify · fastify
< 5.7.3 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-25224
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-25224
Patch
https://github.com/fastify/fastify/commit/eb11156396f6a5fedaceed0140aed2b7f026be37
Vendor Advisory
https://github.com/fastify/fastify/security/advisories/GHSA-mrq3-vjjr-p77c
Permissions Required
https://hackerone.com/reports/3524779
More from fastify
8.8
CVE-2022-41919
Fastify is a web framework with minimal overhead and plugin architecture
8.1
CVE-2026-84504
fastify vulnerable to request body replacement via an async validation result collision
7.5
CVE-2026-84428
fastify vulnerable to header validation bypass via incomplete schema case normalization
7.5
CVE-2026-84469
fastify vulnerable to request validation bypass via skipped boolean false schemas
7.5
CVE-2026-76169
fastify vulnerable to authentication bypass via malformed URLs reaching encapsulated not-found handlers