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Timing based private key exposure in Bouncy Castle

Moderate severity GitHub Reviewed Published Aug 13, 2021 to the GitHub Advisory Database • Updated Jul 17, 2025

Package

nuget BouncyCastle (NuGet)

Affected versions

< 1.8.7

Patched versions

1.8.7
maven org.bouncycastle:bc-fips (Maven)
<= 1.0.2
1.0.2.1
maven org.bouncycastle:bcprov-ext-jdk15on (Maven)
< 1.66
1.66
maven org.bouncycastle:bcprov-ext-jdk16 (Maven)
< 1.66
1.66
maven org.bouncycastle:bcprov-jdk14 (Maven)
< 1.66
1.66
maven org.bouncycastle:bcprov-jdk15 (Maven)
< 1.66
1.66
maven org.bouncycastle:bcprov-jdk15on (Maven)
< 1.66
1.66
maven org.bouncycastle:bcprov-jdk15to18 (Maven)
< 1.66
1.66
maven org.bouncycastle:bcprov-jdk16 (Maven)
< 1.66
1.66

Description

Bouncy Castle BC Java before 1.66, BC C# .NET before 1.8.7, BC-FJA before 1.0.2.1, BC before 1.66, BC-FNA before 1.0.1.1 have a timing issue within the EC math library that can expose information about the private key when an attacker is able to observe timing information for the generation of multiple deterministic ECDSA signatures.

References

Published by the National Vulnerability Database May 20, 2021
Reviewed May 21, 2021
Published to the GitHub Advisory Database Aug 13, 2021
Last updated Jul 17, 2025

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(71st percentile)

Weaknesses

Observable Discrepancy

The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not. Learn more on MITRE.

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently. Learn more on MITRE.

CVE ID

CVE-2020-15522

GHSA ID

GHSA-6xx3-rg99-gc3p

Source code

No known source code

Credits

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