CVE-2021-45450

What it actually does

The vulnerability allows psa_cipher_generate_iv and psa_cipher_encrypt to bypass PSA crypto policy checks or enable oracle-based decryption when the output buffer resides in memory regions accessible to an untrusted application.

Why it matters to the business

Organizations relying on Mbed TLS for cryptographic operations face potential exposure of sensitive encrypted data, which can undermine confidentiality protections in embedded, IoT, and application security controls; the issue has been public for years with low but stable exploitability signals and broad library adoption.

How an attack unfolds

An attacker identifies an application using vulnerable Mbed TLS versions that places output buffers in untrusted memory, then supplies crafted inputs to psa_cipher_generate_iv or psa_cipher_encrypt to either bypass policy restrictions or obtain plaintext via decryption oracle behavior.

How to fix it

Upgrade mbed-tls/mbedtls to the fixed commit 8b3f26a5ac38d4fdccbc5c5366229f3e01dafcc0 or later releases 2.28.0 and 3.1.0; rebuild and redeploy all dependent applications after updating the library.

How to confirm the fix worked

Verify the installed Mbed TLS version or commit hash matches a fixed release; perform regression testing of PSA cipher operations with untrusted memory buffers to confirm policy enforcement and absence of oracle behavior.

Typical attack path

1. Identify target application using affected Mbed TLS library
2. Locate or influence code paths invoking psa_cipher_generate_iv or psa_cipher_encrypt with output buffers in attacker-accessible memory
3. Supply malicious inputs that trigger policy bypass or decryption oracle responses
4. Extract sensitive plaintext or bypass intended cryptographic protections

How to detect it

Review application logs and memory access patterns around PSA cipher function calls for unusual buffer handling or repeated oracle-style queries; correlate with known vulnerable library versions in deployed binaries.

What your security team should do

• Immediately inventory all products and builds depending on Mbed TLS and schedule upgrades to the fixed commit or newer releases
• Prioritize patching in any externally facing or high-value cryptographic deployments given the network-attack vector and confidentiality impact
• Update dependency management and CI pipelines to enforce minimum Mbed TLS versions going forward