CVE-2020-20949

Bleichenbacher's attack on PKCS #1 v1.5 padding for RSA in STM32 cryptographic firmware library...

5.9 Medium

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: High
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: High
Integrity: None
Availability: None

Exploit likelihood

0.94%Down 0.6 points since Apr 14, 2021

What each source reports

NVD Score used 5.9

Record: CVE-2020-20949
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS 2.0: 4.3 MediumAV:N/AC:M/Au:N/C:P/I:N/A:N
Weakness: CWE-327
Updated: 2026-11-02

CVE List No score

Record: CVE-2020-20949
Updated: 2026-11-02

EUVDEUVD-2020-13728 No score

Record: EUVD-2020-13728
Updated: 2026-11-02

GitHub AdvisoriesGHSA-7p98-xcgc-gwhj 5.9

Bleichenbacher's attack on PKCS #1 v1.5 padding for RSA in STM32 cryptographic firmware library...

Record: GHSA-7p98-xcgc-gwhj
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness: CWE-326, CWE-327
Updated: 2026-11-02

Affected products

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History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2020-20949 is a medium vulnerability (CVSS 5.9) in Ietf Public Key Cryptography Standards \#1, published January 20, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.94%, the 61st percentile. No source names a fixed version.