CVE-2020-12403

Name: CVE-2020-12403
Creator: NVD / NIST
Published: 2021-05-27T19:15:07.953+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.1/10EPSS 1.54%

Last modified Jun 17, 2026

CVE-2020-12403 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. 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. EPSS estimates a 1.54% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

9.1/10

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

EPSS Probability

1.54%

71.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Mozilla	Nss	< 3.55

References

https://bugzilla.redhat.com/show_bug.cgi?id=1868931Issue Tracking, Patch, Third Party Advisory
https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/NSS_3.55_release_notesRelease Notes, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2023/02/msg00021.html
https://security.netapp.com/advisory/ntap-20230324-0006/
https://bugzilla.redhat.com/show_bug.cgi?id=1868931Issue Tracking, Patch, Third Party Advisory
https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/NSS_3.55_release_notesRelease Notes, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2023/02/msg00021.html
https://security.netapp.com/advisory/ntap-20230324-0006/

Timeline

Published: May 27, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-12403?

How severe is CVE-2020-12403?

CVE-2020-12403 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 1.54% probability of exploitation in the next 30 days.

How do I fix CVE-2020-12403?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-12403?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST