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Fencer Vulns
high 7.5

CVE-2021-33560 json

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 at…

published 2021-06-08 5 y ago modified 2026-10-14 26 d ago also EUVD-2021-20252 , JLSEC-2026-123

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.4%
EPSS 2.4% chance of exploitation in 30 days, percentile 83%
public exploits
0
none known

Summary

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.

Patch / fix

  • julia Libgcrypt_jll 1.8.11+0
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • libgcrypt20 Debian 14, Debian 13, Debian 12 1.9.4-2

debian advisories DEBIAN-CVE-2021-33560

  • libgcrypt20 Ubuntu 18.04 LTS 1.8.1-4ubuntu1.3
  • libgcrypt20 Ubuntu 20.04 LTS 1.8.5-5ubuntu1.1
  • libgcrypt20 Ubuntu 22.04 LTS 1.8.7-5ubuntu2
  • libgcrypt20 Ubuntu Pro 16.04 LTS 1.6.5-2ubuntu0.6+esm1
  • libgcrypt20 Ubuntu Pro FIPS-updates 18.04 LTS 1.8.1-4ubuntu1.fips.3
  • libgcrypt20 Ubuntu Pro FIPS-updates 20.04 LTS, Ubuntu Pro FIPS 20.04 LTS 1.8.5-5ubuntu1.fips.1.1

ubuntu advisories UBUNTU-CVE-2021-33560

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libgcrypt RHEL 8 1.8.5-6.el8

red hat advisories RHSA-2021:4409

  • libgcrypt SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +9 more 1.8.2-8.39.1
  • libgcrypt SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +11 more 1.6.1-16.77.1
  • libgcrypt SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 1.8.2-6.52.1
  • libgcrypt SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 1.5.0-0.26.6.1

suse advisories SUSE-SU-2021:2157-1SUSE-SU-2021:2156-1SUSE-SU-2021:2155-1SUSE-SU-2021:14751-1

  • libgcrypt openSUSE Tumbleweed 1.9.4-1.2
  • libgcrypt openSUSE Leap 15.3 1.8.2-8.39.1
  • libgcrypt openSUSE Leap 15.2 1.8.2-lp152.17.3.1

opensuse advisories openSUSE-SU-2024:10941-1openSUSE-SU-2021:2157-1openSUSE-SU-2021:0919-1

  • libgcrypt AlmaLinux 8 1.8.5-6.el8

almalinux advisories ALSA-2021:4409

  • libgcrypt Rocky Linux 8 1.8.5-6.el8

rocky linux advisories RLSA-2021:4409

  • libgcrypt Alpine 3.13, Alpine 3.12, Alpine 3.11 1.8.8-r0
  • libgcrypt Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 1.9.4-r0

alpine advisories ALPINE-CVE-2021-33560

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libgcrypt Arch Linux 1.9.3-1
  • lib32-libgcrypt Arch Linux 1.9.3-1

arch linux advisories AVG-2011AVG-2012

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-33560 updated cvss 7.5

libgcrypt: mishandles ElGamal encryption because it lacks exponent blinding to address a side-channel attack against mpi_powm

  • Red Hat Enterprise Linux 6 libgcrypt Red Hat Enterprise Linux 7 libgcrypt
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux BaseOS (v. 8) libgcrypt 1.8.5-6.el8
    fixed: vendor fix RHSA-2021:4409
  • Red Hat Enterprise Linux 9 libgcrypt
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-23-348-10 updated cvss 7.5

Siemens SIMATIC S7-1500

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.0, < 3.1.5
    affected: fixed in V3.1.5, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
11 mo ago

Exploit prediction

2.37% chance of exploitation in the next 30 days, higher than 83% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:P/I:N/A:N
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
julia Libgcrypt_jll
<1.8.11+0
1.8.11+0

Affected products

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.