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NVD / CVE Program· CNA mitre

CVE-2021-33560: 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 att

Noroxi assessment

Priority: Monitor (action score 31/100)

  • Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
  • Probability of exploitation in the next 30 days: 2.3% (FIRST EPSS); higher than 83.8% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: libgcrypt (AlmaLinux:8) 1.8.5-6.el8; libgcrypt-devel (AlmaLinux:8) 1.8.5-6.el8; libgcrypt (Alpine:v3.11) 1.8.8-r0.
  • Mentioned 5 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to libgcrypt (AlmaLinux:8) 1.8.5-6.el8; libgcrypt-devel (AlmaLinux:8) 1.8.5-6.el8; libgcrypt (Alpine:v3.11) 1.8.8-r0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 7.5 · v3.1—Proof of concept Fix available
Published
Jun 8, 2021
Updated
Oct 14, 2026
EPSS
2.3% · 83th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 2.3%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
7.5
CNA · mitre
7.5
agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • Proof of concept exists, no weaponized module
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-33560

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
gnupglibgcrypt
debiandebian linux
fedoraprojectfedora
oraclecommunications cloud native core binding support function
oraclecommunications cloud native core network function cloud native environment
oraclecommunications cloud native core network repository function
oraclecommunications cloud native core network slice selection function
oraclecommunications cloud native core service communication proxy

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux9.0
  • fedoraproject fedora33
  • fedoraproject fedora34
  • gnupg libgcrypt1.9.0 and later · before 1.9.3
  • gnupg libgcryptbefore 1.8.8
  • oracle communications cloud native core binding support function1.11.0
  • oracle communications cloud native core network function cloud native environment1.10.0
  • oracle communications cloud native core network function cloud native environment1.9.0
  • oracle communications cloud native core network repository function1.14.0
  • oracle communications cloud native core network repository function1.15.0
  • oracle communications cloud native core network repository function1.15.1
  • oracle communications cloud native core network slice selection function1.8.0
  • oracle communications cloud native core service communication proxy1.15.0

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8libgcryptbefore 1.8.5-6.el81.8.5-6.el8
AlmaLinux:8libgcrypt-develbefore 1.8.5-6.el81.8.5-6.el8
Alpine:v3.11libgcryptfrom 1.9.0 · before 1.8.8-r01.8.8-r0
Alpine:v3.14libgcryptfrom 1.9.0 · before 1.9.4-r01.9.4-r0
Debian:12libgcrypt20before 1.9.4-21.9.4-2
openSUSE:Leap 15.2libgcryptbefore 1.8.2-lp152.17.3.11.8.2-lp152.17.3.1
openSUSE:Leap 15.3libgcryptbefore 1.8.2-8.39.11.8.2-8.39.1
openSUSE:Tumbleweedlibgcryptbefore 1.9.4-1.21.9.4-1.2
Red Hat:enterprise_linux:8::baseoslibgcryptbefore 0:1.8.5-6.el80:1.8.5-6.el8
Red Hat:enterprise_linux:8::baseoslibgcrypt-debuginfobefore 0:1.8.5-6.el80:1.8.5-6.el8
Red Hat:enterprise_linux:8::baseoslibgcrypt-debugsourcebefore 0:1.8.5-6.el80:1.8.5-6.el8
Red Hat:enterprise_linux:8::baseoslibgcrypt-develbefore 0:1.8.5-6.el80:1.8.5-6.el8
Red Hat:enterprise_linux:8::baseoslibgcrypt-devel-debuginfobefore 0:1.8.5-6.el80:1.8.5-6.el8
Rocky Linux:8libgcryptbefore 0:1.8.5-6.el80:1.8.5-6.el8
SUSE:HPE Helion OpenStack 8libgcryptbefore 1.6.1-16.77.11.6.1-16.77.1
SUSE:Linux Enterprise High Performance Computing 15-ESPOSlibgcryptbefore 1.8.2-6.52.11.8.2-6.52.1
SUSE:Linux Enterprise Module for Basesystem 15 SP2libgcryptbefore 1.8.2-8.39.11.8.2-8.39.1
SUSE:Linux Enterprise Point of Sale 11 SP3libgcryptbefore 1.5.0-0.26.6.11.5.0-0.26.6.1

Same product

gnupg: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-3345_gcry_md_block_write in cipher/hash-common.c in Libgcrypt version 1.9.0 has a heap-based buffer overflow when the digest final function sets
    31Monitor
  • CVE-2018-6829cipher/elgamal.c in Libgcrypt through 1.8.2, when used to encrypt messages directly, improperly encodes plaintexts, which allows attackers t
    31Monitor
  • CVE-2017-0379Libgcrypt before 1.8.1 does not properly consider Curve25519 side-channel attacks, which makes it easier for attackers to discover a secret
    31Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2017-7526Jul 26, 2018 · libgcrypt before version 1.7.8 is vulnerable to a cache side-channel attack resulting into a complete break of RSA-1024 while using the left
    28Monitor
  • ← EarlierCVE-2019-12904Jun 20, 2019 · In Libgcrypt 1.8.4, the C implementation of AES is vulnerable to a flush-and-reload side-channel attack because physical addresses are avail
    24Monitor
  • Later →CVE-2021-40528Sep 6, 2021 · The ElGamal implementation in Libgcrypt before 1.9.4 allows plaintext recovery because, during interaction between two cryptographic librari
    23Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:libgcrypt1.8.5-6.el8 · AlmaLinux:8Package registry (OSV)
almalinux:libgcrypt-devel1.8.5-6.el8 · AlmaLinux:8Package registry (OSV)
alpine:libgcrypt1.8.8-r0 · Alpine:v3.11Package registry (OSV)
debian:libgcrypt201.9.4-2 · Debian:12Package registry (OSV)
opensuse:libgcrypt1.8.2-lp152.17.3.1 · openSUSE:Leap 15.2Package registry (OSV)
red hat:libgcrypt0:1.8.5-6.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:libgcrypt-debuginfo0:1.8.5-6.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:libgcrypt-debugsource0:1.8.5-6.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:libgcrypt-devel0:1.8.5-6.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:libgcrypt-devel-debuginfo0:1.8.5-6.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
rocky linux:libgcrypt0:1.8.5-6.el8 · Rocky Linux:8Package registry (OSV)
suse:libgcrypt1.5.0-0.26.6.1 · SUSE:Linux Enterprise Point of Sale 11 SP3Package registry (OSV)

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Proof-of-concept repository on GitHub ×1

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHubstars:12021-07-16

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. First PoC+38 d
  3. TodayNov 4, 2026+1975 d

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
none
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-203 · Observable Discrepancy

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (12 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records