A flaw was found in the way CHACHA20-POLY1305 was implemented in NSS in versions before 3.55. When using multi-part Chacha20, it could cause out-of-bounds reads. This issue was fixed by explicitly disabling multi-part ChaCha20 (which was not functioning correctly) and strictly enforcing tag length. The highest threat from this vulnerability is to confidentiality and system availability.
https://bugzilla.redhat.com/show_bug.cgi?id=1868931
https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/NSS_3.55_release_notes
Source: MITRE
Published: 2021-05-27
Updated: 2021-06-09
Type: CWE-125
Base Score: 6.4
Vector: AV:N/AC:L/Au:N/C:P/I:N/A:P
Impact Score: 4.9
Exploitability Score: 10
Severity: MEDIUM
Base Score: 9.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Impact Score: 5.2
Exploitability Score: 3.9
Severity: CRITICAL