ElGamal key disclosure via unblinded exponentiation
Published Jun 8, 2021 · Updated Dec 3, 2025
Libgcrypt before 1.8.8 and 1.9.x before 1.9.3 allows remote attackers to recover ElGamal private-key information via side-channel observations. The ElGamal encryption path calls mpi_powm without exponent blinding and uses an unsuitable window size, allowing timing leakage during modular exponentiation. Exploitation requires repeated observations of encryption operations; the bounded consequence is disclosure of secret exponent information rather than data modification or service interruption.
Summary
What happened
Libgcrypt before 1.8.8 and 1.9.x before 1.9.3 allows remote attackers to recover ElGamal private-key information via side-channel observations. The ElGamal encryption path calls mpi_powm without exponent blinding and uses an unsuitable window size, allowing timing leakage during modular exponentiation. Exploitation requires repeated observations of encryption operations; the bounded consequence is disclosure of secret exponent information rather than data modification or service interruption.
The record
- CVE
- CVE-2021-33560
- Published
- Jun 8, 2021
- Updated
- Dec 3, 2025
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-203, CWE-325, T1040
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 8, 2021CVE publishedPublication date reported by the CVE source.
- Dec 3, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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