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CVE-2021-40530

The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during...

5.9 MediumFix available

The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
None
Availability
None

Exploit likelihood

1.16%Up 0.3 points since Sep 7, 2021
90%50%10%1%

What each source reports

NVD Score used 5.9

The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP.

Record
CVE-2021-40530
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS 2.0
2.6 LowAV:N/AC:H/Au:N/C:P/I:N/A:N
Weakness
CWE-327
Updated
2026-11-02
CVE List No score

The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP.

Record
CVE-2021-40530
Updated
2026-11-02
EUVDEUVD-2021-27705 No score

The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP.

Record
EUVD-2021-27705
Updated
2026-11-03
GitHub AdvisoriesGHSA-p3r9-6fhw-hgv8 No score

The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during...

The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP.

Record
GHSA-p3r9-6fhw-hgv8
Weakness
CWE-327
Updated
2026-11-02
OSV 5.9

The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP.

Record
CVE-2021-40530
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSVDEBIAN-CVE-2021-40530 5.9

The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP.

Record
DEBIAN-CVE-2021-40530
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSVUBUNTU-CVE-2021-40530 5.9

The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP.

Record
UBUNTU-CVE-2021-40530
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSVMGASA-2021-0468 No score

Updated libcryptopp packages fix security vulnerability

The ElGamal implementation in Crypto++ through 8.5 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP. (CVE-2021-40530)

Record
MGASA-2021-0468
Updated
2026-11-02
OSVopenSUSE-SU-2024:10933-1 No score

libcryptopp-devel-8.6.0-1.1 on GA media

These are all security issues fixed in the libcryptopp-devel-8.6.0-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2024:10933-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
libcrypto++
Debian:12
before 8.6.0-1
8.6.0-1
libcrypto++
Debian:13
before 8.6.0-1
8.6.0-1
libcrypto++
Debian:14
before 8.6.0-1
8.6.0-1
libcryptopp
Mageia:8
before 8.2.0-2.1.mga8
8.2.0-2.1.mga8
libcrypto++
Ubuntu:Pro:14.04:LTS
All versions, plus listed versions
5.6.1-65.6.1-6+deb8u1build0.14.04.15.6.1-6+deb8u3build0.14.04.15.6.1-6+deb8u3ubuntu0.1~esm1
None known
libcrypto++
Ubuntu:Pro:16.04:LTS
All versions, plus listed versions
5.6.1-85.6.1-95.6.1-9ubuntu0.15.6.1-9ubuntu0.1+esm1
None known
libcrypto++
Ubuntu:18.04:LTS
All versions, plus listed versions
5.6.4-8
None known
libcrypto++
Ubuntu:20.04:LTS
All versions, plus listed versions
5.6.4-95.6.4-9build1
None known
libcrypto++
Ubuntu:22.04:LTS
All versions, plus listed versions
8.4.0-18.6.0-2ubuntu1
None known
libcrypto++
Ubuntu:24.04:LTS
All versions, plus listed versions
8.8.0-18.9.0-18.9.0-1.18.9.0-1.1build1
None known
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Affected packages
PackageAffectedFixed
libcrypto++
Ubuntu:25.10
All versions, plus listed versions
8.9.0-1.1build18.9.0-2
None known
libcrypto++
Ubuntu:26.10
All versions, plus listed versions
8.9.0-2build18.9.0-3
None known
libcrypto++
Ubuntu:26.04:LTS
All versions, plus listed versions
8.9.0-28.9.0-2build1
None known
libcryptopp
openSUSE:Tumbleweed
From an advisory covering 2 CVEs
before 8.6.0-1.1
8.6.0-1.1

History

History
RecordedChangedSources
affected, facts
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-40530 is a medium vulnerability (CVSS 5.9) in Cryptopp Crypto\+\+, published September 6, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.16%, the 67th percentile. Fixed in libcrypto++ 8.6.0-1.

References

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