CVE-2021-40528
Published: 6 September 2021
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.
Notes
| Author | Note |
|---|---|
| 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. |
Priority
Status
| Package | Release | Status |
|---|---|---|
|
libgcrypt20 Launchpad, Ubuntu, Debian |
impish |
Released
(1.8.7-5ubuntu2)
|
| jammy |
Released
(1.8.7-5ubuntu2)
|
|
| trusty |
Does not exist
|
|
| upstream |
Released
(1.9.4-2)
|
|
| bionic |
Released
(1.8.1-4ubuntu1.3)
|
|
| focal |
Released
(1.8.5-5ubuntu1.1)
|
|
| hirsute |
Released
(1.8.7-2ubuntu2.1)
|
|
| xenial |
Released
(1.6.5-2ubuntu0.6+esm1)
Available with Ubuntu Pro or Ubuntu Pro (Infra-only) |
|
| kinetic |
Released
(1.8.7-5ubuntu2)
|
|
| lunar |
Released
(1.8.7-5ubuntu2)
|
|
|
Patches: upstream: https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commit;h=3462280f2e23e16adf3ed5176e0f2413d8861320 (1.9x) upstream: https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commit;h=707c3c5c511ee70ad0e39ec613471f665305fbea (1.8x) |
||
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score | 5.9 |
| 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
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-40528
- 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://ubuntu.com/security/notices/USN-5080-1
- https://ubuntu.com/security/notices/USN-5080-2
- NVD
- Launchpad
- Debian