How severe is CVE-2020-20949?

CVE-2020-20949 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2020-20949 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-20949?

CVE-2020-20949 primarily affects St Stm32cubef0. In total, 22 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-20949?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2020-20949 published?

CVE-2020-20949 was published on 2021-01-20 and last updated on 2026-07-05.

CVE-2020-20949

CVE-2020-20949 is a medium-severity vulnerability in St Stm32cubef0 with a CVSS 3.x base score of 5.9. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-327.

Key facts

Severity: Medium (CVSS 3.x base score 5.9)
CVSS v2: 4.3
EPSS exploit prediction: 1% (56th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-327
Affected product: St Stm32cubef0
Published: 2021-01-20
Last modified: 2026-07-05

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.

Frequently asked questions

What is CVE-2020-20949?: 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.
How severe is CVE-2020-20949?: CVE-2020-20949 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2020-20949 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-20949?: CVE-2020-20949 primarily affects St Stm32cubef0. In total, 22 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-20949?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2020-20949 published?: CVE-2020-20949 was published on 2021-01-20 and last updated on 2026-07-05.

References

Affected products (22)

cpe:2.3:a:st:stm32cubef0:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubef1:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubef2:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubef3:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubef4:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubef7:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubeg0:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubeg4:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubeh7:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubeide:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubel0:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubel1:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubel4:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubel4\+:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubel5:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubemonitor:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubemp1:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubemx:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubeprogrammer:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubewb:-:*:*:*:*:*:*:*
cpe:2.3:a:st:stm32cubewl:-:*:*:*:*:*:*:*
cpe:2.3:a:ietf:public_key_cryptography_standards_\#1:1.5:*:*:*:*:*:*:*

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