CVE-2025-66442
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB...
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.
- Record
CVE-2025-66442- CVSS 3.1
- 5.1 Medium
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-385
- Updated
- 2026-11-02
EUVDEUVD-2025-209171
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.
- Record
EUVD-2025-209171- CVSS 3.1
- 5.1 Medium
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-56v8-wv3m-qgg6
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB...
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.
- Record
GHSA-56v8-wv3m-qgg6- CVSS 3.1
- 5.1 Medium
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-385
- Updated
- 2026-11-02
NVD
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.
- Record
CVE-2025-66442- CVSS 3.1
- 5.1 Medium
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-385
- Updated
- 2026-11-04
OSV
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.
- Record
CVE-2025-66442- CVSS 3.1
- 5.1 Medium
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-07
OSVDEBIAN-CVE-2025-66442
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.
- Record
DEBIAN-CVE-2025-66442- CVSS 3.1
- 5.1 Medium
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-05
OSVJLSEC-2026-463
Mbed TLS timing side channel in RSA and CBC/ECB decryption
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.
- Record
JLSEC-2026-463- CVSS 3.1
- 5.1 Medium
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2025-66442
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.
- Record
UBUNTU-CVE-2025-66442- CVSS 3.1
- 5.1 Medium
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
mbedtlsDebian:12 |
All versions, plus listed versions 2.28.3-12.28.4-12.28.5-12.28.6-12.28.7-1 Show 18 moreShow less2.28.7-1.12.28.7-1.1~exp12.28.8-13.6.0-13.6.0-23.6.0-33.6.2-13.6.2-23.6.2-33.6.3-13.6.4-13.6.4-23.6.5-0.13.6.5-0.1~deb13u13.6.6-0.13.6.6-0.1~deb13u13.6.7-23.6.7-3 |
None known |
mbedtlsDebian:13 |
All versions, plus listed versions 3.6.4-23.6.5-0.13.6.5-0.1~deb13u13.6.6-0.13.6.6-0.1~deb13u13.6.7-23.6.7-3 |
None known |
mbedtlsDebian:14 |
All versions, plus listed versions 3.6.4-23.6.5-0.13.6.5-0.1~deb13u13.6.6-0.13.6.6-0.1~deb13u13.6.7-23.6.7-3 |
None known |
MbedTLS_jllJulia |
All versions | None known |
mbedtlsUbuntu:16.04:LTS |
All versions, plus listed versions 2.1.2-12.2.0-12.2.1-12.2.1-22.2.1-2ubuntu0.12.2.1-2ubuntu0.22.2.1-2ubuntu0.3 |
None known |
mbedtlsUbuntu:Pro:18.04:LTS |
All versions, plus listed versions 2.5.1-1ubuntu12.6.0-12.7.0-22.8.0-12.8.0-1ubuntu0.1~esm1 |
None known |
mbedtlsUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 2.16.2-12.16.3-12.16.4-1ubuntu22.16.4-1ubuntu2+esm1 |
None known |
mbedtlsUbuntu:Pro:22.04:LTS |
All versions, plus listed versions 2.16.9-0.1ubuntu12.16.11-0.1ubuntu12.16.11-0.32.28.0-12.28.0-1build12.28.0-1ubuntu0.1~esm1 |
None known |
mbedtlsUbuntu:Pro:24.04:LTS |
All versions, plus listed versions 2.28.3-12.28.6-1ubuntu12.28.7-1ubuntu12.28.7-1.1ubuntu12.28.8-12.28.8-1ubuntu0.1~esm1 |
None known |
mbedtlsUbuntu:25.10 |
All versions, plus listed versions 3.6.2-3ubuntu1 |
None known |
mbedtlsUbuntu:26.10 |
All versions, plus listed versions 3.6.5-0.1ubuntu23.6.6-0.1ubuntu13.6.7-3ubuntu1 |
None known |
mbedtlsUbuntu:26.04:LTS |
All versions, plus listed versions 3.6.2-3ubuntu13.6.5-0.1ubuntu13.6.5-0.1ubuntu2 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected | NVD, OSV | |
| facts | OSV | |
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2025-66442 is a medium vulnerability (CVSS 5.1) in Arm Mbed Tls, published April 1, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.28%, the 20th percentile. No source names a fixed version.
References
github.com/Mbed-TLS/mbedtls/releases
mbed-tls.readthedocs.io/en/latest/security-advisories
nvd.nist.gov/vuln/detail/CVE-2025-66442