CVE-2024-29040 in tpm2-tss
Summary
by MITRE • 06/29/2024
This repository hosts source code implementing the Trusted Computing Group's (TCG) TPM2 Software Stack (TSS). The JSON Quote Info returned by Fapi_Quote has to be deserialized by Fapi_VerifyQuote to the TPM Structure `TPMS_ATTEST`. For the field `TPM2_GENERATED magic` of this structure any number can be used in the JSON structure. The verifier can receive a state which does not represent the actual, possibly malicious state of the device under test. The malicious device might get access to data it shouldn't, or can use services it shouldn't be able to. This issue has been patched in version 4.1.0.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 10/13/2024
The vulnerability identified as CVE-2024-29040 resides within the Trusted Computing Group's TPM2 Software Stack (TSS) implementation, specifically affecting the Fapi_Quote and Fapi_VerifyQuote functions that handle TPM quote operations. This security flaw manifests in a critical deserialization issue where the JSON Quote Info structure returned by Fapi_Quote can be manipulated during the verification process by Fapi_VerifyQuote. The vulnerability stems from the improper validation of the TPM2_GENERATED magic field within the TPMS_ATTEST structure, which allows attackers to inject arbitrary values that bypass normal verification mechanisms.
The technical flaw represents a direct violation of the principle of least privilege and integrity verification within the TPM2 framework. According to CWE-284, this vulnerability enables improper access control by allowing malicious actors to manipulate the verification state of TPM attestations. The flaw operates at the interface between JSON serialization and TPM structure validation, where the verifier accepts potentially malicious state information that does not accurately reflect the actual device state. This creates a scenario where a compromised device could present false attestation data that appears legitimate to the verification system, effectively undermining the trust model that TPMs are designed to provide.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential data exposure and service abuse within the TPM ecosystem. An attacker exploiting this flaw could gain unauthorized access to sensitive data that should be protected by TPM attestation mechanisms, or could potentially utilize TPM services that should be restricted to legitimate users or systems. The vulnerability essentially allows for the creation of false trust relationships, where malicious devices can appear to be authentic TPM components within a secure system. This represents a significant threat to the security posture of systems relying on TPM2 for hardware-based security assurances, particularly in environments where TPM attestation is used for authentication, integrity verification, or access control decisions.
The remediation for CVE-2024-29040 was implemented in version 4.1.0 of the TSS, which addressed the deserialization process by enforcing stricter validation of the TPM2_GENERATED magic field and other critical components within the TPMS_ATTEST structure. This fix aligns with ATT&CK technique T1552.001, which involves the exploitation of credential access mechanisms, by ensuring proper validation of attestation data. The patch likely introduced additional cryptographic validation checks and state integrity verification mechanisms that prevent arbitrary values from being accepted during the quote verification process. Organizations should immediately upgrade to version 4.1.0 or later to mitigate this vulnerability and restore the intended security guarantees of TPM2 attestation mechanisms.
This vulnerability demonstrates the critical importance of proper input validation in security-critical systems and highlights the potential for subtle flaws in cryptographic libraries to undermine fundamental security assumptions. The issue exemplifies how even well-established security standards like those from the Trusted Computing Group can contain implementation flaws that expose systems to sophisticated attacks. The vulnerability's resolution through version 4.1.0 underscores the need for continuous security auditing of cryptographic implementations and the importance of maintaining up-to-date security patches in enterprise environments that rely on TPM2 technology for hardware security.