CVE-2021-43398

Exp

Crypto++ (aka Cryptopp) 8.6.0 and earlier contains a timing leakage in MakePublicKey(). There is a clear correlation between execution time and private key length, which may cause disclosure of the length information of the private key. This might allow attackers to conduct timing attacks. NOTE: this report is disputed by the vendor and multiple third parties. The execution-time differences are intentional. A user may make a choice of a longer key as a tradeoff between strength and performance. In making this choice, the amount of information leaked to an adversary is of infinitesimal value

Published: 2021-11-04 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-43398 is rated High Exploit Risk (64.6/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.90%). 2 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +1.48% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-43398

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-43398

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.42% 1.90% +1.48%
2 2026-02-16 0.50% 0.42% -0.08%
3 2025-04-19 — 0.50% —

Full EPSS history (13 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-43398

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:P/I:N/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-43398

OS Trackers for CVE-2021-43398

vendor priority summary link
suse medium CVE-2021-43398 severity moderate: SUSE including 4 source package names (libcryptopp, libcryptopp-devel, libcryptopp5_6_5, libcryptopp8_6_0), 40 product×package rows across 18 product lines (SUSE CaaS Platform 4.0, SUSE Enterprise Storage 6, … (18 product lines)): Will Not Fix 40. https://www.suse.com/security/cve/CVE-2021-43398/
ubuntu medium CVE-2021-43398 medium priority: Ubuntu including 1 source packages (libcrypto++), 12 status rows across 12 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, trusty, upstream, xenial): not-affected 6, ignored 5, needs-triage 1. https://ubuntu.com/security/CVE-2021-43398

Affected software / configurations for CVE-2021-43398

Vendor Product Version Raw CPE
cryptopp crypto\+\+ <= 8.6.0 cpe:2.3:a:cryptopp:crypto\+\+:*:*:*:*:*:*:*:*

References for CVE-2021-43398

URL Tags
https://cryptopp.com Vendor Advisory
https://github.com/weidai11/cryptopp/issues/1080 Exploit Third Party Advisory
https://github.com/weidai11/cryptopp/issues/1080#issuecomment-996492222 Exploit Issue Tracking Third Party Advisory
cvelogic Threat Intelligence