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Date: Mon, 27 Sep 2021 17:16:25 +0000
From: Jeremy Stanley <>
Subject: [OSSA-2021-002] Nova: Open Redirect in noVNC proxy (CVE-2021-3654)

OSSA-2021-002: Open Redirect in noVNC proxy

:Date: July 29, 2021
:CVE: CVE-2021-3654

- Nova: <21.2.3, >=22.0.0 <22.2.3, >=23.0.0 <23.0.3

Swe Aung, Shahaan Ayyub, and Salman Khan with the Monash University
Cyber Security team reported a vulnerability affecting Nova's noVNC
proxying implementation which exposed access to a well-known
redirect behavior in the Python standard library's
http.server.SimpleHTTPRequestHandler and thus noVNC's
WebSockifyRequestHandler which uses it. By convincing a user to
follow a specially-crafted novncproxy URL, the user could be
redirected to an unrelated site under control of the attacker in an
attempt to convince them to divulge credentials or other sensitive
data. All Nova deployments with novncproxy enabled are affected.

The initial fix did not take into account the possibility of bypass
using exactly three slashes. This update provides a more thorough
revised fix for the issue. The affected versions list has been
updated to indicate versions expected to include the newer solution.

- (Train)
- (errata 1) (Train)
- (Ussuri)
- (errata 1) (Ussuri)
- (Victoria)
- (errata 1) (Victoria)
- (Wallaby)
- (errata 1) (Wallaby)
- (Xena)
- (errata 1) (Xena)

- Swe Aung from Monash University Cyber Security team (CVE-2021-3654)
- Shahaan Ayyub from Monash University Cyber Security team (CVE-2021-3654)
- Salman Khan from Monash University Cyber Security team (CVE-2021-3654)


- The stable/train branch is under extended maintenance and will
  receive no new point releases, but a patch for it is provided as a

OSSA History
- 2021-09-27 - Errata 1
- 2021-07-29 - Original Version

Jeremy Stanley

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