Vulnerability · Published Sep 6, 2021 · Assigned by mitre
CVE-2021-40528
Medium 5.9
In plain English
A medium-severity broken cryptography in the libgcrypt package (AlmaLinux). There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.4% (higher than 73% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
The ElGamal implementation in Libgcrypt before 1.9.4 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:8 | libgcrypt | 1.8.5-7.el8_6 | ALSA-2022:5311 |
| AlmaLinux:8 | libgcrypt-devel | 1.8.5-7.el8_6 | ALSA-2022:5311 |
| Debian:12 | libgcrypt20 | 1.8.7-6 | DEBIAN-CVE-2021-40528 |
| Debian:13 | libgcrypt20 | 1.8.7-6 | DEBIAN-CVE-2021-40528 |
| Debian:14 | libgcrypt20 | 1.8.7-6 | DEBIAN-CVE-2021-40528 |
| Rocky Linux:8 | libgcrypt | 0:1.8.5-7.el8_6 | RLSA-2022:5311 |
| Ubuntu:22.04:LTS | libgcrypt20 | 1.8.7-5ubuntu2 | UBUNTU-CVE-2021-40528 |
Affected products (as reported)
Weakness: CWE-327 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
References
- https://eprint.iacr.org/2021/923
- https://ibm.github.io/system-security-research-updates/2021/07/20/insecurity-elgamal-pt1
- https://ibm.github.io/system-security-research-updates/2021/09/06/insecurity-elgamal-pt2
- https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git%3Ba=commit%3Bh=3462280f2e23e16adf3ed5176e0f2413d8861320
- GLSA-202210-13 vendor-advisory