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CVE-2021-33560: Libgcrypt before 1.8.8 and 1.9.x before 1.9.3 mishandles ElGamal encryption because it lacks exponent blind...

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 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Libgcrypt had a cryptographic side-channel weakness in ElGamal handling. Systems using vulnerable versions could leak confidential information from operations such as OpenPGP ElGamal use. The issue is high severity, but the provided sources do not show confirmed active exploitation.

Executive priority

Treat this as a targeted confidentiality risk for systems performing affected cryptographic operations. Patch through normal security-update channels, with higher priority for mail, key-management, and encryption workflows.

Technical view

Before 1.8.8 and 1.9.x before 1.9.3, Libgcrypt lacked exponent blinding for mpi_powm and selected an inappropriate window size. The CVE maps this to CWE-325 and CVSS 7.5, with confidentiality impact only.

Likely exposure

Exposure is most likely where Linux distributions, packaged applications, or vendor products include vulnerable Libgcrypt and perform ElGamal/OpenPGP cryptographic operations. Debian, Fedora, Oracle, and Gentoo references indicate downstream package impact.

Exploitation context

The bundle describes a side-channel attack condition, not a public exploit. CISA KEV is false in the provided data, so active exploitation is not established from these sources.

Researcher notes

Evidence supports a Libgcrypt ElGamal side-channel fix path, but the provided affected-product metadata is generic. Validate exposure by package version and actual cryptographic usage, not by product name alone.

Mitigation direction

  • Upgrade Libgcrypt to 1.8.8, 1.9.3, or later.
  • Apply relevant Debian, Fedora, Gentoo, or Oracle security updates.
  • Prioritize systems handling OpenPGP ElGamal keys or sensitive cryptographic workloads.
  • Check vendor guidance for bundled or statically linked Libgcrypt copies.
  • Rotate exposed secrets only if investigation indicates key material compromise.

Validation and detection

  • Inventory Libgcrypt versions across hosts, containers, and appliances.
  • Flag versions before 1.8.8 and 1.9.x before 1.9.3.
  • Identify applications using Libgcrypt for ElGamal or OpenPGP operations.
  • Confirm fixed package status against applicable vendor advisories.
  • Review cryptographic service logs for unusual access patterns, where available.
Prepared
Confidence
high
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-325: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2021-33560 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
13Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N3.93.6Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2021-33560Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

CWE-325

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-325 · source CWE mapping

Missing Cryptographic Step

Missing Cryptographic Step represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs