HOMEVULNERABILITIESCVE-2020-20949
MEDIUM

CVE-2020-20949

CWE-327Published: January 20, 2021· Updated: Jul 9, 2026

5.9
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2020-20949 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), with a CVSS base score of 5.9.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityHigh
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityNone
AvailabilityNone
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected Vendors & Products

ietf1 product(s)
public key cryptography standards \#1
st21 product(s)
stm32cubef0stm32cubef1stm32cubef2stm32cubef3stm32cubef4stm32cubef7stm32cubeg0stm32cubeg4stm32cubeh7stm32cubeidestm32cubel0stm32cubel1+9
Source: NVD CPE · 22 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttp://archiv.infsec.ethz.ch/education/fs08/secsem/bleichenbacher98.pdf
ADVISORYhttps://bi-zone.medium.com/silence-will-fall-or-how-it-can-take-2-years-to-get-your-vuln-registered-e6134846f5bb
ADVISORYhttps://www.st.com/en/embedded-software/x-cube-cryptolib.html
ADVISORYhttp://archiv.infsec.ethz.ch/education/fs08/secsem/bleichenbacher98.pdf
ADVISORYhttps://bi-zone.medium.com/silence-will-fall-or-how-it-can-take-2-years-to-get-your-vuln-registered-e6134846f5bb
ADVISORYhttps://www.st.com/en/embedded-software/x-cube-cryptolib.html

All References (6)

→
http://archiv.infsec.ethz.ch/education/fs08/secsem/bleichenbacher98.pdfTechnical Description · Third Party Advisory
→
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
→
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

Quick Facts

CVE IDCVE-2020-20949
CVSS Score5.9 / 10
SeverityMEDIUM
WeaknessCWE-327
CISA KEVNo
Affected2 vendor(s)
PublishedJan 20, 2021

Related CVEs (CWE-327)

CVE-2026-50086
10.0
CVE-2025-54426
9.9
CVE-2024-28980
9.8
CVE-2021-45696
9.8
CVE-2023-34039
9.8
CVE-2014-8687
9.8

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2020-20949 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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