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Vulnerability record · CVE-2021-43527 · published 8 December 2021

CVE-2021-43527: Mozilla nss out-of-bounds write vulnerability

Mozilla · Nss

NSS (Network Security Services) versions prior to 3.73 or 3.68.1 ESR are vulnerable to a heap overflow when handling DER-encoded DSA or RSA-PSS signatures. Applications using NSS for handling signatures encoded within CMS, S/MIME, PKCS \#7, or PKCS \#12 are likely to be impacted. Applications using NSS for certificate validation or other TLS, X.509, OCSP or CRL functionality may be impacted, depending on how they configure NSS. *Note: This vulnerability does NOT impact Mozilla Firefox.* However, email clients and PDF viewers that use NSS for signature verification, such as Thunderbird, LibreOffice, Evolution and Evince are believed to be impacted. This vulnerability affects NSS < 3.73 and NSS < 3.68.1.

9.8 CVSS 3.1 Critical EPSS 18% · top 3.0% CWE-787 · Out-of-bounds write
9.8CVSS 3.1 base score, v2 7.5
18%EPSS exploitation probability, 30 days
NoNot in CISA KEV
10Affected product versions listed by NVD
18References
17 Jun 2026Last modified by NVD

Description

NSS (Network Security Services) versions prior to 3.73 or 3.68.1 ESR are vulnerable to a heap overflow when handling DER-encoded DSA or RSA-PSS signatures. Applications using NSS for handling signatures encoded within CMS, S/MIME, PKCS \#7, or PKCS \#12 are likely to be impacted. Applications using NSS for certificate validation or other TLS, X.509, OCSP or CRL functionality may be impacted, depending on how they configure NSS. *Note: This vulnerability does NOT impact Mozilla Firefox.* However, email clients and PDF viewers that use NSS for signature verification, such as Thunderbird, LibreOffice, Evolution and Evince are believed to be impacted. This vulnerability affects NSS < 3.73 and NSS < 3.68.1.

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

Affected products

10 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugzilla.mozilla.org/show_bug.cgi?id=1737470 Issue TrackingPermissions RequiredVendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-594438.pdf Third Party Advisory
https://ftp.mozilla.org/pub/security/nss/releases/NSS_3_68_1_RTM/ Vendor Advisory
https://ftp.mozilla.org/pub/security/nss/releases/NSS_3_73_RTM/ Vendor Advisory
https://security.gentoo.org/glsa/202212-05 Third Party Advisory
https://security.netapp.com/advisory/ntap-20211229-0002/ Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2021-51/ Vendor Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html PatchThird Party Advisory
https://www.starwindsoftware.com/security/sw-20220802-0001/ Third Party Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1737470 Issue TrackingPermissions RequiredVendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-594438.pdf Third Party Advisory
https://ftp.mozilla.org/pub/security/nss/releases/NSS_3_68_1_RTM/ Vendor Advisory
https://ftp.mozilla.org/pub/security/nss/releases/NSS_3_73_RTM/ Vendor Advisory
https://security.gentoo.org/glsa/202212-05 Third Party Advisory
https://security.netapp.com/advisory/ntap-20211229-0002/ Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2021-51/ Vendor Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html PatchThird Party Advisory
https://www.starwindsoftware.com/security/sw-20220802-0001/ Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-43527), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.