CVE-2021-43527 in Fujitsu M10-1
Summary
by MITRE • 12/09/2021
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.
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Analysis
by VulDB Data Team • 05/16/2025
The vulnerability identified as CVE-2021-43527 represents a critical heap overflow condition within the Network Security Services (NSS) cryptographic library that affects versions prior to 3.73 and 3.68.1 Extended Support Release. This heap overflow occurs specifically during the processing of DER-encoded DSA or RSA-PSS signatures, making it a significant concern for applications that rely on NSS for cryptographic operations. The vulnerability stems from inadequate bounds checking when parsing signature structures, creating opportunities for attackers to manipulate memory allocation patterns through crafted malicious signatures. The affected NSS versions demonstrate a failure in input validation mechanisms that should have prevented excessive memory allocation during signature processing. This flaw particularly impacts applications that utilize NSS for handling CMS, S/MIME, PKCS#7, or PKCS#12 signature formats, as these protocols commonly employ DSA and RSA-PSS signature algorithms. The vulnerability's classification aligns with CWE-121, heap-based buffer overflow, which is categorized under the broader category of memory safety issues in software development practices.
The operational impact of this vulnerability extends beyond the typical scope of cryptographic libraries, affecting a wide range of applications that depend on NSS for security operations. Email clients such as Thunderbird, PDF viewers like Evince, office suites including LibreOffice, and email management tools like Evolution are all potentially vulnerable due to their reliance on NSS for signature verification processes. The vulnerability's exploitation could lead to arbitrary code execution, system compromise, or denial of service conditions depending on how the affected applications handle the memory corruption. Applications using NSS for certificate validation, TLS operations, X.509 processing, OCSP, or CRL functionality may also be at risk based on their specific NSS configuration and usage patterns. This creates a cascading security risk where a single vulnerable component can affect multiple security-sensitive applications across different software domains. The ATT&CK framework categorizes this vulnerability under T1059.007 for command and scripting interpreter, as exploitation could enable attackers to execute arbitrary commands through memory corruption techniques.
Mitigation strategies for CVE-2021-43527 primarily focus on immediate version upgrades to NSS 3.73 or 3.68.1 ESR releases, which contain the necessary patches to address the heap overflow conditions. Organizations should prioritize updating all affected applications that utilize NSS, particularly those handling digital signatures or certificate validation operations. Security teams should implement comprehensive inventory tracking to identify all systems using vulnerable NSS versions and establish remediation schedules. Network monitoring solutions should be configured to detect anomalous signature processing patterns that might indicate exploitation attempts. Additionally, application developers should review their NSS integration code to ensure proper error handling and input validation are implemented. The vulnerability's impact on non-Mozilla products like Thunderbird and LibreOffice underscores the importance of maintaining updated cryptographic libraries across all security-sensitive applications. Organizations should also consider implementing runtime protections such as address space layout randomization and stack canaries to mitigate potential exploitation scenarios. Security controls should include regular vulnerability scanning to identify systems running outdated NSS versions and automated patch management processes to ensure timely remediation of similar future vulnerabilities.