What’s Vulnerable › Vulnerabilities

CVE-2020-12403

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-05-27 · updated 2026-06-17
• Weakness: CWE-125

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.

Affected products

• Mozilla NSS: before 3.55 — fixed in 3.55

How to fix

Upgrade to a fixed version: Mozilla NSS 3.55. Check the vendor advisory for mitigations.

References

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

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