CVE-2021-24119

RSA key-information disclosure via base64 cache side channel

Published Jul 14, 2021 · Updated Nov 3, 2025

Side-channel exposure in Mbed TLS before 2.26.0 allows local users to extract information about RSA private keys during PEM decoding. The base64 decoder uses a key-dependent lookup table, so its cache-line access pattern reveals information while it decodes PEM-encoded keys. Exploitation requires administrator control capable of single-stepping an isolated workload and monitoring cache activity, as demonstrated against Intel SGX.

CVSS severity4.9
Medium
EPSS probability1.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Side-channel exposure in Mbed TLS before 2.26.0 allows local users to extract information about RSA private keys during PEM decoding. The base64 decoder uses a key-dependent lookup table, so its cache-line access pattern reveals information while it decodes PEM-encoded keys. Exploitation requires administrator control capable of single-stepping an isolated workload and monitoring cache activity, as demonstrated against Intel SGX.

The record

CVE
CVE-2021-24119
Published
Jul 14, 2021
Updated
Nov 3, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-203
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Jul 14, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.9NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
4.0NIST NVDAV:N/AC:L/Au:S/C:P/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-203Observable Discrepancy

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo