CVE-2020-20949

Name: CVE-2020-20949
Creator: NVD / NIST
Published: 2021-01-20T16:15:14.007+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.9/10EPSS 0.92%

Last modified Jun 17, 2026

CVE-2020-20949 is a medium-severity vulnerability rated 5.9/10 on the CVSS scale. Bleichenbacher's attack on PKCS #1 v1.5 padding for RSA in STM32 cryptographic firmware library software expansion for STM32Cube (UM1924). The vulnerability can allow one to use Bleichenbacher's oracle attack to decrypt an encrypted ciphertext by making successive queries to the server using the vulnerable library, resulting in remote information disclosure.. EPSS estimates a 0.92% chance of exploitation in the next 30 days.

Description

Bleichenbacher's attack on PKCS #1 v1.5 padding for RSA in STM32 cryptographic firmware library software expansion for STM32Cube (UM1924). The vulnerability can allow one to use Bleichenbacher's oracle attack to decrypt an encrypted ciphertext by making successive queries to the server using the vulnerable library, resulting in remote information disclosure.

Metrics

CVSS 3.1

5.9/10

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

EPSS Probability

0.92%

55.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-327

Affected Software

Vendor	Product	Versions
St	Stm32cubef0	All versions
St	Stm32cubef1	All versions
St	Stm32cubef2	All versions
St	Stm32cubef3	All versions
St	Stm32cubef4	All versions
St	Stm32cubef7	All versions
St	Stm32cubeg0	All versions
St	Stm32cubeg4	All versions
St	Stm32cubeh7	All versions
St	Stm32cubeide	All versions
St	Stm32cubel0	All versions
St	Stm32cubel1	All versions
St	Stm32cubel4	All versions
St	Stm32cubel4\+	All versions
St	Stm32cubel5	All versions
St	Stm32cubemonitor	All versions
St	Stm32cubemp1	All versions
St	Stm32cubemx	All versions
St	Stm32cubeprogrammer	All versions
St	Stm32cubewb	All versions
St	Stm32cubewl	All versions
Ietf	Public Key Cryptography Standards \#1	1.5

References

http://archiv.infsec.ethz.ch/education/fs08/secsem/bleichenbacher98.pdfTechnical Description, Third Party Advisory
http://st.comProduct
http://x-cube-cryptolib.comBroken Link
https://bi-zone.medium.com/silence-will-fall-or-how-it-can-take-2-years-to-get-your-vuln-registered-e6134846f5bbTechnical Description, Third Party Advisory
https://www.st.com/en/embedded-software/x-cube-cryptolib.htmlThird Party Advisory
http://archiv.infsec.ethz.ch/education/fs08/secsem/bleichenbacher98.pdfTechnical Description, Third Party Advisory
http://st.comProduct
http://x-cube-cryptolib.comBroken Link
https://bi-zone.medium.com/silence-will-fall-or-how-it-can-take-2-years-to-get-your-vuln-registered-e6134846f5bbTechnical Description, Third Party Advisory
https://www.st.com/en/embedded-software/x-cube-cryptolib.htmlThird Party Advisory

Timeline

Published: Jan 20, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-20949?

How severe is CVE-2020-20949?

CVE-2020-20949 has a CVSS score of 5.9/10 (MEDIUM severity). The EPSS model estimates a 0.92% probability of exploitation in the next 30 days.

How do I fix CVE-2020-20949?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-20949?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST