CVE-2021-43527: Critical severity mozilla nss vulnerability
A flaw was found in the way NSS verifies certificates. That will happen both when client reads the Certificate message from the server or when server is configured to ask for client certificates and then receives one.
Firefox is not vulnerable as it uses the mozilla::pkix for certificate verification. Crucially, NSS fully parses the certificate before any other checks, so disabled signature methods or certificate types don't impact exploitability.
Any TLS and DTLS client that does use NSS built in certificate verification routines is vulnerable as well as any server that has certificate based client authentication enabled.
But the issue is not limited to TLS, any applications that use certificate verification are vulnerable, S/MIME is impacted too.
Other sources
A remote code execution flaw was found in the way NSS verifies certificates. This flaw allows an attacker posing as an SSL/TLS server to trigger this issue in a client application compiled with NSS when it tries to initiate an SSL/TLS connection. Similarly, a server application compiled with NSS, which processes client certificates, can receive a malicious certificate via a client, triggering the flaw. The highest threat to this vulnerability is confidentiality, integrity, as well as system availability.
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.
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.
Affected Software
Remediation
Patch Available
Information
Event History
Parent advisories
This vulnerability appears in the following advisories.
Frequently Asked Questions
What is CVE-2021-43527?
CVE-2021-43527 is a remote code execution vulnerability in NSS (Network Security Services) versions prior to 3.73 or 3.68.1 ESR.
What is the severity of CVE-2021-43527?
The severity of CVE-2021-43527 is critical with a CVSS score of 9.8.
Which applications are likely to be impacted by CVE-2021-43527?
Applications using NSS for handling signatures encoded within CMS, S/MIME, PKCS #7, or PKCS #12 are likely to be impacted by CVE-2021-43527.
How can I fix CVE-2021-43527?
To fix CVE-2021-43527, upgrade NSS to version 3.73.0 or 3.68.1 ESR.
Where can I find more information about CVE-2021-43527?
You can find more information about CVE-2021-43527 at the following references: [Link 1](https://bugzilla.mozilla.org/show_bug.cgi?id=1737470), [Link 2](https://ftp.mozilla.org/pub/security/nss/releases/NSS_3_73_RTM/), [Link 3](https://ftp.mozilla.org/pub/security/nss/releases/NSS_3_68_1_RTM/).