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Mbed TlsApplication · Trustedfirmware

CVE-2024-45157

MEDIUM · 5.1 CVSS v3.1 Published 2024-09-05
Fix available
A fix is available. Upgrade to 2.28.9 / 3.6.1 or later.
See remediation →
56/100
Remediation priority · Elevated
No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An issue was discovered in Mbed TLS before 2.28.9 and 3.x before 3.6.1, in which the user-selected algorithm is not used. Unlike previously documented, enabling MBEDTLS_PSA_HMAC_DRBG_MD_TYPE does not cause the PSA subsystem to use HMAC_DRBG: it uses HMAC_DRBG only when MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG and MBEDTLS_CTR_DRBG_C are disabled.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In Mbed TLS before versions 2.28.9 and 3.6.1, the PSA crypto subsystem does not correctly honor the MBEDTLS_PSA_HMAC_DRBG_MD_TYPE configuration option. Instead of using HMAC_DRBG when this option is enabled, the subsystem only uses HMAC_DRBG when BOTH MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG and MBEDTLS_CTR_DRBG_C are disabled. This causes users who expect HMAC_DRBG to unknowingly use CTR_DRBG instead, potentially leading to weaker random number generation than intended.

MitigationUpgrade Mbed TLS to version 2.28.9, 3.6.1, or later. For immediate mitigation, ensure MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG is enabled if HMAC_DRBG is required, and carefully review build configurations to verify the intended DRBG implementation is actually being used.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Mbed TlsApplication
Affected:>= 2.26.0, < 2.28.9>= 3.2.0, < 3.6.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the installed Mbed TLS version
    Check the version header file (e.g., include/mbedtls/version.h) or the library binary metadata for the exact version number
    Affected if The version is >= 2.26.0 and < 2.28.9, or >= 3.2.0 and < 3.6.1
  2. Verify if MBEDTLS_PSA_HMAC_DRBG_MD_TYPE is configured
    Inspect the build configuration files (mbedtls_config.h or config.h) or preprocessor defines for MBEDTLS_PSA_HMAC_DRBG_MD_TYPE being set to a message digest algorithm identifier (e.g., MBEDTLS_MD_SHA256)
    Affected if This option is enabled and the version falls in the affected range
  3. Check the status of MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG
    Search the build configuration for MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG being defined/enabled
    Affected if This option is disabled (commented out or not defined)
  4. Check the status of MBEDTLS_CTR_DRBG_C
    Search the build configuration for MBEDTLS_CTR_DRBG_C being defined/enabled
    Affected if This option is enabled
  5. Determine if the problematic combination exists
    Review the configuration: if MBEDTLS_PSA_HMAC_DRBG_MD_TYPE is set, MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG is disabled, and MBEDTLS_CTR_DRBG_C is enabled, then HMAC_DRBG is NOT being used despite the expectation
    Affected if All three conditions are true: HMAC_DRBG MD type configured, external RNG disabled, CTR_DRBG enabled - this means the weaker CTR_DRBG is being used instead of HMAC_DRBG

You are affected if you have an affected Mbed TLS version, enabled MBEDTLS_PSA_HMAC_DRBG_MD_TYPE, but have MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG disabled and MBEDTLS_CTR_DRBG_C enabled, resulting in unintended CTR_DRBG usage instead of HMAC_DRBG.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.28.9 / 3.6.1 or later
Fixed in 2.28.93.6.1
Interim mitigation

Upgrade Mbed TLS to version 2.28.9, 3.6.1, or later. For immediate mitigation, ensure MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG is enabled if HMAC_DRBG is required, and carefully review build configurations to verify the intended DRBG implementation is actually being used.

Recommended fix High confidence

Mbed TLS 2.28.9 or 3.6.1 (depending on your major version branch)

  1. 1. Identify the currently installed Mbed TLS version using your package manager or by checking the version.h header file
  2. 2. For Mbed TLS 2.x versions: upgrade to version 2.28.9 or later
  3. 3. For Mbed TLS 3.x versions: upgrade to version 3.6.1 or later
  4. 4. If using a package manager (apt, yum, brew, etc.), update the package to the latest available version that includes the fixes
  5. 5. If building from source, download the appropriate release from the official Mbed TLS repository (github.com/ARMmbed/mbedtls)
  6. 6. Rebuild any applications that link against Mbed TLS libraries
  7. 7. Verify the upgrade by checking that MBEDTLS_VERSION_NUMBER macro reflects the new version
  8. 8. Test that the PSA crypto subsystem now correctly uses HMAC_DRBG when MBEDTLS_PSA_HMAC_DRBG_MD_TYPE is enabled
Caveat Review release notes for any behavioral changes between your current version and 2.28.9/3.6.1, particularly around RNG configuration options

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Mbed Tls Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,696.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2024-45157 in production — separate from our analysis above.

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