AIKIDO-2026-675639
Mbed-TLS.mbedtls is vulnerable to Observable Timing Discrepancy
53
Medium Risk
This Affects:
Mbed-TLS.mbedtlsTL;DR
When decrypting with block cipher modes that use padding, Mbed TLS translates internal cipher error codes into PSA error codes in a way that is not constant time. A local attacker who can request decryptions and observe timing through shared resources such as caches or the branch predictor learns whether padding was valid, forming a padding oracle. This allows partial or full recovery of plaintext encrypted with CBC-PKCS7. The fix removes the timing difference and adds a padding-aware finish function for safer error handling.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and your application decrypts untrusted ciphertext with a padded CBC or ECB mode through the PSA API.
Background info
Mbed-TLS.mbedtls is vulnerable to Observable Timing Discrepancy in versions 1.0.0 - 3.6.4.
How to fix this
Upgrade the Mbed-TLS.mbedtls library to the patch version.
Links
GitHub Release
Other
mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2025-10-invalid-padding-error/mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories/
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