CVE-2023-40271 in Firmware-M
Summary
by MITRE • 09/08/2023
In Trusted Firmware-M through TF-Mv1.8.0, for platforms that integrate the CryptoCell accelerator, when the CryptoCell PSA Driver software Interface is selected, and the Authenticated Encryption with Associated Data Chacha20-Poly1305 algorithm is used, with the single-part verification function (defined during the build-time configuration phase) implemented with a dedicated function (i.e., not relying on usage of multipart functions), the buffer comparison during the verification of the authentication tag does not happen on the full 16 bytes but just on the first 4 bytes, thus leading to the possibility that unauthenticated payloads might be identified as authentic. This affects TF-Mv1.6.0, TF-Mv1.6.1, TF-Mv1.7.0, and TF-Mv1.8.
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Analysis
by VulDB Data Team • 01/27/2026
The vulnerability identified as CVE-2023-40271 represents a critical cryptographic flaw within Trusted Firmware-M versions 1.6.0 through 1.8.0, specifically affecting platforms utilizing the CryptoCell accelerator with the PSA Driver software interface. This issue manifests when the Authenticated Encryption with Associated Data Chacha20-Poly1305 algorithm is implemented using single-part verification functions rather than multipart functions. The flaw resides in the verification process where the authentication tag comparison is truncated to only the first 4 bytes instead of the full 16-byte tag, creating a significant security weakness that undermines the integrity protection mechanisms. The vulnerability affects a substantial portion of the TF-M ecosystem, spanning multiple minor releases including the widely used 1.6.0, 1.6.1, 1.7.0, and 1.8.0 versions, indicating a persistent issue that has remained unaddressed across several iterations of the firmware.
The technical implementation of this vulnerability stems from a buffer comparison error in the cryptographic verification routine for the Chacha20-Poly1305 algorithm. When the single-part verification function is invoked, the system performs an authentication tag comparison that only examines the first four bytes of the 16-byte authentication tag rather than the complete tag. This truncated comparison creates a scenario where an attacker could potentially manipulate the payload data without detection, as the verification process would incorrectly accept the modified data as authentic. The flaw specifically impacts the CryptoCell PSA Driver implementation and is directly tied to build-time configuration decisions that determine whether single-part or multipart verification functions are used. This represents a clear violation of cryptographic best practices where the security of the authentication mechanism is compromised due to an implementation error that reduces the effective security strength of the authentication tag from 128 bits to just 32 bits.
The operational impact of this vulnerability extends beyond simple cryptographic weakness, as it fundamentally undermines the security assurances provided by the Chacha20-Poly1305 algorithm in embedded systems environments. An attacker exploiting this vulnerability could successfully inject malicious payloads into authenticated communications without detection, potentially leading to data corruption, unauthorized access, or complete system compromise depending on the application context. The vulnerability affects not just individual devices but entire deployment ecosystems where TF-M is integrated, particularly in IoT and embedded security applications where the CryptoCell accelerator is commonly used. This weakness creates a potential attack surface that could be exploited in various scenarios including secure boot processes, secure communication channels, and cryptographic operations that rely on the integrity protection provided by the authentication tag. The impact is particularly severe in environments where the integrity of cryptographic operations is paramount for system security and where the assumption of authenticated data integrity is fundamental to the security architecture.
Mitigation strategies for CVE-2023-40271 must focus on immediate patching of affected TF-M versions to address the buffer comparison implementation error in the Chacha20-Poly1305 verification process. Organizations should prioritize upgrading to TF-M versions that contain the fix for this specific vulnerability, ensuring that the complete 16-byte authentication tag comparison is implemented correctly. The recommended approach involves verifying build-time configurations to ensure that multipart verification functions are used instead of single-part functions when the Chacha20-Poly1305 algorithm is required, or implementing proper fix for the buffer comparison routine. Security teams should conduct comprehensive assessments of systems utilizing affected TF-M versions to identify potential exploitation risks and implement additional monitoring for unauthorized modifications to authenticated data. This vulnerability aligns with CWE-295 which addresses improper certificate validation and CWE-310 which covers cryptographic issues, while also mapping to ATT&CK techniques related to credential access and privilege escalation through cryptographic manipulation. Organizations should also consider implementing additional security controls such as integrity monitoring and anomaly detection systems to detect potential exploitation attempts that could leverage this vulnerability.