NSS PKCS#11 Parsing Flaw Enables DoS and Information Disclosure
A vulnerability in NSS's handling of PKCS#11 URI escape sequences could allow attackers to crash the library or leak sensitive data. Ubuntu has released security updates to address the issue across multiple distributions.
TL;DR
- NSS incorrectly parses PKCS#11 URI escape sequences, creating a denial-of-service vector
- Attackers may exploit the flaw to extract sensitive information from affected systems
- The vulnerability affects cryptographic operations relying on NSS for certificate and key handling
- Ubuntu patch USN-8481-1 resolves the parsing defect across supported releases
The Network Security Services (NSS) library, a critical component for cryptographic operations and certificate validation in many Linux distributions and applications, contains a parsing vulnerability in its PKCS#11 URI handling. Researcher Haruto Kimura identified improper escape sequence processing that could be exploited by attackers.
This flaw presents two distinct security risks: denial-of-service conditions through NSS crashes, and potential exposure of sensitive cryptographic material. Organizations running Ubuntu systems should prioritize applying the released security update to prevent exploitation.
Technical Details of the Vulnerability
- NSS fails to correctly parse escape sequences in PKCS#11 URIs, a standard for hardware security module and key storage references
- Malformed URI inputs can trigger unhandled exceptions or memory corruption within the NSS library
- The vulnerability affects any application or service that uses NSS for cryptographic operations and processes untrusted PKCS#11 URIs
Security Impact and Remediation
- Denial-of-service attacks can crash services dependent on NSS, disrupting authentication and encryption workflows
- Information disclosure may allow attackers to read sensitive data from memory during parsing failures
- Ubuntu patch USN-8481-1 corrects the escape sequence handling logic in affected NSS versions
- System administrators should apply updates immediately to all Ubuntu systems running vulnerable NSS releases
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