| Name | CVE-2021-33560 |
| Description | Libgcrypt before 1.8.8 and 1.9.x before 1.9.3 mishandles ElGamal encryption because it lacks exponent blinding to address a side-channel attack against mpi_powm, and the window size is not chosen appropriately. This, for example, affects use of ElGamal in OpenPGP. |
| Source | CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
Vulnerable and fixed packages
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|
| libgcrypt20 (PTS) | bullseye | 1.8.7-6 | vulnerable |
| bookworm | 1.10.1-3 | fixed |
| sid, trixie | 1.11.0-6 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|
| libgcrypt20 | source | (unstable) | 1.9.4-2 | | | |
Notes
[bullseye] - libgcrypt20 <no-dsa> (Minor issue)
[buster] - libgcrypt20 <no-dsa> (Minor issue)
[stretch] - libgcrypt20 <no-dsa> (Minor issue)
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;a=commit;h=e8b7f10be275bcedb5fc05ed4837a89bfd605c61 (1.9.x)
Related to CVE-2021-33560, but not a duplicate. Unfortunately scope of CVE-2021-33560 and
CVE-2021-40528 got switched at some point, and CVE-2021-33560 referring to the blinding
hardening. We keep the original association as per 2021-09-19 (until MITRE clarifies on
a query).