CVE-2021-40528
Publication date 6 September 2021
Last updated 18 August 2025
Ubuntu priority
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.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| libgcrypt20 | 25.10 questing |
Fixed 1.8.7-5ubuntu2
|
| 25.04 plucky |
Fixed 1.8.7-5ubuntu2
|
|
| 24.04 LTS noble |
Fixed 1.8.7-5ubuntu2
|
|
| 22.04 LTS jammy |
Fixed 1.8.7-5ubuntu2
|
|
| 20.04 LTS focal |
Fixed 1.8.5-5ubuntu1.1
|
|
| 18.04 LTS bionic |
Fixed 1.8.1-4ubuntu1.3
|
|
| 16.04 LTS xenial |
Fixed 1.6.5-2ubuntu0.6+esm1
|
|
| 14.04 LTS trusty | Not in release |
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mdeslaur
The commits below reference CVE-2021-33560, but they appear to actually be for this CVE, which was issued later. The original CVE was switched later on to the exponent blinding issue instead.
Patch details
| Package | Patch details |
|---|---|
| libgcrypt20 |
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score |
5.9 · Medium
|
| Attack vector | Network |
| Attack complexity | High |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity impact | None |
| Availability impact | None |
| Vector | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N |
References
Related Ubuntu Security Notices (USN)
- USN-5080-1
- Libgcrypt vulnerabilities
- 16 September 2021
- USN-5080-2
- Libgcrypt vulnerabilities
- 16 September 2021