Critical 9.1Published May 27, 2021

CVE-2020-12403A flaw was found in the way CHACHA20-POLY1305 was implemented in NSS in versions before 3.55.

Updated under an hour ago (Nov 2, 2026, 12:23 AM ET)

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No exploitation reported and no EPSS estimate yet.

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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.

CVSS: 9.1 CRITICAL (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Weakness (CWE): CWE-125
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Not given
NVD analysis: Modified
Record last updated: Jun 16, 2026
First seen by InfoSec Signals: Nov 1, 2026

Affected products

Affected products

mozilla nss mozilla:nss	before 3.55	NVD

References

References

https://bugzilla.redhat.com/show_bug.cgi?id=1868931	issue-tracking, patch, third-party-advisory
https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/NSS_3.55_release_notes	release-notes, vendor-advisory
https://lists.debian.org/debian-lts-announce/2023/02/msg00021.html
https://security.netapp.com/advisory/ntap-20230324-0006/

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.