CVE-2021-21293 Information

Description

blaze is a Scala library for building asynchronous pipelines with a focus on network IO. All servers running blaze-core before version 0.14.15 are affected by a vulnerability in which unbounded connection acceptance leads to file handle exhaustion. Blaze accepts connections unconditionally on a dedicated thread pool. This has the net effect of amplifying degradation in services that are unable to handle their current request load since incoming connections are still accepted and added to an unbounded queue. Each connection allocates a socket handle which drains a scarce OS resource. This can also confound higher level circuit breakers which work based on detecting failed connections. The vast majority of affected users are using it as part of http4s-blaze-server <= 0.21.16. http4s provides a mechanism for limiting open connections but is enforced inside the Blaze accept loop after the connection is accepted and the socket opened. Thus the limit only prevents the number of connections which can be simultaneously processed not the number of connections which can be held open. The issue is fixed in version 0.14.15 for \NIO1SocketServerGroup. A \maxConnections\ parameter is added with a default value of 512. Concurrent connections beyond this limit are rejected. To run unbounded which is not recommended set a negative number. The \NIO2SocketServerGroup\ has no such setting and is now deprecated. There are several possible workarounds described in the refrenced GitHub Advisory GHSA-xmw9-q7x9-j5qc.

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Reference

https://github.com/http4s/blaze/commit/4f786177f9fb71ab272f3a5f6c80bca3e5662aa1 https://github.com/http4s/blaze/security/advisories/GHSA-xmw9-q7x9-j5qc https://github.com/http4s/http4s/security/advisories/GHSA-xhv5-w9c5-2r2w

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

NONE

Base Score

HIGH

Base Severity

7.5