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Vulnerability details: VCID-r5mn-4ntx-aaam
Vulnerability ID VCID-r5mn-4ntx-aaam
Aliases CVE-2021-36647
Summary Use of a Broken or Risky Cryptographic Algorithm in the function mbedtls_mpi_exp_mod() in lignum.c in Mbed TLS Mbed TLS all versions before 3.0.0, 2.27.0 or 2.16.11 allows attackers with access to precise enough timing and memory access information (typically an untrusted operating system attacking a secure enclave such as SGX or the TrustZone secure world) to recover the private keys used in RSA.
Status Published
Exploitability 0.5
Weighted Severity 4.2
Risk 2.1
Affected and Fixed Packages Package Details
Weaknesses (1)
CWE-327 Use of a Broken or Risky Cryptographic Algorithm
System Score Found at
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epss 0.00056 https://api.first.org/data/v1/epss?cve=CVE-2021-36647
epss 0.00056 https://api.first.org/data/v1/epss?cve=CVE-2021-36647
epss 0.00056 https://api.first.org/data/v1/epss?cve=CVE-2021-36647
epss 0.00056 https://api.first.org/data/v1/epss?cve=CVE-2021-36647
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epss 0.00056 https://api.first.org/data/v1/epss?cve=CVE-2021-36647
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cvssv3.1 4.7 https://github.com/ARMmbed/mbedtls/releases/
ssvc Track https://github.com/ARMmbed/mbedtls/releases/
cvssv3.1 4.7 https://kouzili.com/Load-Step.pdf
ssvc Track https://kouzili.com/Load-Step.pdf
cvssv3 4.7 https://nvd.nist.gov/vuln/detail/CVE-2021-36647
cvssv3.1 4.7 https://nvd.nist.gov/vuln/detail/CVE-2021-36647
cvssv3.1 4.7 https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1
ssvc Track https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2021-36647
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-36647
https://github.com/ARMmbed/mbedtls/releases/
https://kouzili.com/Load-Step.pdf
https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1
cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*
CVE-2021-36647 https://nvd.nist.gov/vuln/detail/CVE-2021-36647
No exploits are available.
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N Found at https://github.com/ARMmbed/mbedtls/releases/
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:N/A:N/T:P/P:M/B:A/M:M/D:T/2025-04-08T20:30:16Z/ Found at https://github.com/ARMmbed/mbedtls/releases/
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N Found at https://kouzili.com/Load-Step.pdf
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:N/A:N/T:P/P:M/B:A/M:M/D:T/2025-04-08T20:30:16Z/ Found at https://kouzili.com/Load-Step.pdf
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-36647
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-36647
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N Found at https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:N/A:N/T:P/P:M/B:A/M:M/D:T/2025-04-08T20:30:16Z/ Found at https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1
Exploit Prediction Scoring System (EPSS)
Percentile 0.04951
EPSS Score 0.00033
Published At March 29, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
There are no relevant records.