cipher/elgamal.c in Libgcrypt through 1.8.2, when used to encrypt messages directly, improperly encodes plaintexts, which allows attackers to obtain sensitive information by reading ciphertext data (i.e., it does not have semantic security in face of a ciphertext-only attack). The Decisional Diffie-Hellman (DDH) assumption does not hold for Libgcrypt's ElGamal implementation.
The MITRE CVE dictionary describes this issue as:
Find out more about CVE-2018-6829 from the MITRE CVE dictionary dictionary and NIST NVD.
This is not a security flaw in libgcrypt. However if an application uses The El-gamal algorithm implemented by libgcrypt in a particular way than the application would be vulnerable to security flaw(s). More detailed explanation is available at: https://lists.gnupg.org/pipermail/gcrypt-devel/2018-February/004401.html
NOTE: The following CVSS v3 metrics and score provided are preliminary and subject to review.
| CVSS3 Base Score | 5.3 |
|---|---|
| CVSS3 Base Metrics | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N |
| Attack Vector | Network |
| Attack Complexity | Low |
| Privileges Required | None |
| User Interaction | None |
| Scope | Unchanged |
| Confidentiality | Low |
| Integrity Impact | None |
| Availability Impact | None |
| Platform | Package | State |
|---|---|---|
| Red Hat Enterprise Linux 7 | libgcrypt | Not affected |
| Red Hat Enterprise Linux 6 | libgcrypt | Not affected |
| Red Hat Enterprise Linux 5 | libgcrypt | Not affected |
Vulmon