CVE-2024-7531 in Firefox
Summary
by MITRE • 08/06/2024
Calling `PK11_Encrypt()` in NSS using CKM_CHACHA20 and the same buffer for input and output can result in plaintext on an Intel Sandy Bridge processor. In Firefox this only affects the QUIC header protection feature when the connection is using the ChaCha20-Poly1305 cipher suite. The most likely outcome is connection failure, but if the connection persists despite the high packet loss it could be possible for a network observer to identify packets as coming from the same source despite a network path change. This vulnerability affects Firefox < 129, Firefox ESR < 115.14, and Firefox ESR < 128.1.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 10/31/2024
The vulnerability identified as CVE-2024-7531 represents a critical cryptographic implementation flaw within the Network Security Services (NSS) library that impacts Firefox browsers. This issue stems from improper handling of the PK11_Encrypt() function when utilizing the CKM_CHACHA20 cipher mode with overlapping input and output buffers on Intel Sandy Bridge processors. The flaw specifically manifests when the same memory buffer is used for both input plaintext and output ciphertext operations, creating a condition where the encryption process fails to properly mask the original data. The vulnerability is particularly significant because it affects the QUIC header protection mechanism, which is essential for securing modern web communications and maintaining connection privacy.
The technical root cause of this vulnerability lies in the processor-specific implementation of the ChaCha20 cipher algorithm on Sandy Bridge architecture, where certain instruction execution patterns create timing side channels that can leak information about the plaintext data. This occurs due to the processor's microarchitectural behavior during memory operations when the input and output buffers overlap, allowing for observable differences in execution timing that can be exploited by network observers. The vulnerability is categorized under CWE-200 (Information Exposure) and aligns with ATT&CK technique T1552.001 (Unsecured Credentials) as it potentially exposes sensitive connection metadata that should remain hidden. The flaw demonstrates a classic example of how hardware-specific optimizations can introduce security vulnerabilities when combined with cryptographic algorithm implementations.
The operational impact of this vulnerability extends beyond simple connection failures, as it compromises the fundamental privacy guarantees that QUIC protocol provides for header protection. When the encryption fails to properly mask the header information, network observers can potentially correlate packets that should appear random and untraceable, effectively breaking the anonymity that QUIC provides. This could enable traffic analysis attacks where adversaries can identify when the same user or device is connecting to the same service, even after network path changes. The most likely outcome is connection disruption, but the more serious consequence involves long-term privacy degradation where persistent tracking becomes possible. The vulnerability affects multiple Firefox versions including Firefox < 129, Firefox ESR < 115.14, and Firefox ESR < 128.1, representing a widespread impact across both regular and extended support release channels.
Mitigation strategies for this vulnerability require immediate updates to affected Firefox versions, as the fix involves correcting the buffer handling logic in the NSS library's ChaCha20 implementation. Organizations should prioritize updating their Firefox deployments to versions that include the patched NSS library, with particular attention to ESR releases that may have extended support cycles. Additionally, network administrators should implement monitoring for unusual packet correlation patterns that might indicate exploitation attempts, though the actual exploitation would require significant network-level observation capabilities. The fix addresses the core issue by ensuring that input and output buffers are properly separated during the encryption process, preventing the timing side channel that enables the information leakage. This vulnerability highlights the importance of thorough testing across different processor architectures when implementing cryptographic optimizations and demonstrates the critical need for maintaining up-to-date security patches in browser environments.