How severe is CVE-2021-43398?

CVE-2021-43398 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2021-43398 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (77th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43398?

CVE-2021-43398 affects Cryptopp Crypto++. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-43398?

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

When was CVE-2021-43398 published?

CVE-2021-43398 was published on 2021-11-04 and last updated on 2026-06-17.

CVE-2021-43398

CVE-2021-43398 is a medium-severity vulnerability in Cryptopp Crypto++ with a CVSS 3.x base score of 5.3. 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-203.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v2: 5.0
EPSS exploit prediction: 2% (77th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-203
Affected product: Cryptopp Crypto++
Published: 2021-11-04
Last modified: 2026-06-17

Description

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

Frequently asked questions

What is CVE-2021-43398?: 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
How severe is CVE-2021-43398?: CVE-2021-43398 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2021-43398 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (77th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43398?: CVE-2021-43398 affects Cryptopp Crypto++. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-43398?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-43398 published?: CVE-2021-43398 was published on 2021-11-04 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:cryptopp:crypto\+\+:*:*:*:*:*:*:*:*

More vulnerabilities in Cryptopp Crypto++

CVE-2023-50981 — High (CVSS 7.5): ModularSquareRoot in Crypto++ (aka cryptopp) through 8.9.0 allows attackers to cause a denial of service (infinite…
CVE-2023-50980 — High (CVSS 7.5): gf2n.cpp in Crypto++ (aka cryptopp) through 8.9.0 allows attackers to cause a denial of service (application crash) via…
CVE-2022-48570 — High (CVSS 7.5): Crypto++ through 8.4 contains a timing side channel in ECDSA signature generation. Function…
CVE-2016-3995 — High (CVSS 7.5): The timing attack protection in Rijndael::Enc::ProcessAndXorBlock and Rijndael::Dec::ProcessAndXorBlock in Crypto++…
CVE-2016-9939 — High (CVSS 7.5): Crypto++ (aka cryptopp and libcrypto++) 5.6.4 contained a bug in its ASN.1 BER decoding routine. The library will…
CVE-2016-7544 — High (CVSS 7.5): Crypto++ 5.6.4 incorrectly uses Microsoft's stack-based _malloca and _freea functions. The library will request a block…

All CVEs affecting Cryptopp Crypto++ →

Other CWE-203 (Observable Discrepancy) vulnerabilities

CVE-2019-25337 — Critical (CVSS 9.8): OwnCloud 8.1.8 contains a username enumeration vulnerability that allows remote attackers to discover user accounts by…
CVE-2026-23519 — Critical (CVSS 9.8): RustCrypto CMOV provides conditional move CPU intrinsics which are guaranteed on major platforms to execute in…
CVE-2025-27667 — Critical (CVSS 9.8): Vasion Print (formerly PrinterLogic) before Virtual Appliance Host 22.0.843 Application 20.0.1923 allows Administrative…
CVE-2024-25714 — Critical (CVSS 9.8): In Rhonabwy through 1.1.13, HMAC signature verification uses a strcmp function that is vulnerable to side-channel…
CVE-2024-25191 — Critical (CVSS 9.8): php-jwt 1.0.0 uses strcmp (which is not constant time) to verify authentication, which makes it easier to bypass…
CVE-2024-25190 — Critical (CVSS 9.8): l8w8jwt 2.2.1 uses memcmp (which is not constant time) to verify authentication, which makes it easier to bypass…

Browse all CWE-203 (Observable Discrepancy) vulnerabilities →