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CVE-2020-26939

Observable Differences in Behavior to Error Inputs in Bouncy Castle

5.3 MediumFix available

In Legion of the Bouncy Castle BC before 1.61 and BC-FJA before 1.0.1.2, attackers can obtain sensitive information about a private exponent because of Observable Differences in Behavior to Error Inputs. This occurs in org.bouncycastle.crypto.encodings.OAEPEncoding. Sending invalid ciphertext that decrypts to a short payload in the OAEP Decoder could result in the throwing of an early exception, potentially leaking some information about the private exponent of the RSA private key performing the encryption.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
None
Availability
None

Exploit likelihood

0.92%Up 0.5 points since Apr 14, 2021
90%50%10%1%

What each source reports

NVD Score used 5.3

In Legion of the Bouncy Castle BC before 1.61 and BC-FJA before 1.0.1.2, attackers can obtain sensitive information about a private exponent because of Observable Differences in Behavior to Error Inputs. This occurs in org.bouncycastle.crypto.encodings.OAEPEncoding. Sending invalid ciphertext that decrypts to a short payload in the OAEP Decoder could result in the throwing of an early exception, potentially leaking some information about the private exponent of the RSA private key performing the encryption.

Record
CVE-2020-26939
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
CVSS 2.0
5.0 MediumAV:N/AC:L/Au:N/C:P/I:N/A:N
Weakness
CWE-203
Updated
2026-11-02
CVE List No score

In Legion of the Bouncy Castle BC before 1.61 and BC-FJA before 1.0.1.2, attackers can obtain sensitive information about a private exponent because of Observable Differences in Behavior to Error Inputs. This occurs in org.bouncycastle.crypto.encodings.OAEPEncoding. Sending invalid ciphertext that decrypts to a short payload in the OAEP Decoder could result in the throwing of an early exception, potentially leaking some information about the private exponent of the RSA private key performing the encryption.

Record
CVE-2020-26939
Updated
2026-11-02
EUVDEUVD-2021-0779 No score

In Legion of the Bouncy Castle BC before 1.61 and BC-FJA before 1.0.1.2, attackers can obtain sensitive information about a private exponent because of Observable Differences in Behavior to Error Inputs. This occurs in org.bouncycastle.crypto.encodings.OAEPEncoding. Sending invalid ciphertext that decrypts to a short payload in the OAEP Decoder could result in the throwing of an early exception, potentially leaking some information about the private exponent of the RSA private key performing the encryption.

Record
EUVD-2021-0779
Updated
2026-11-03
GitHub AdvisoriesGHSA-72m5-fvvv-55m6 5.3

Observable Differences in Behavior to Error Inputs in Bouncy Castle

In Legion of the Bouncy Castle BC before 1.55 and BC-FJA before 1.0.2, attackers can obtain sensitive information about a private exponent because of Observable Differences in Behavior to Error Inputs. This occurs in org.bouncycastle.crypto.encodings.OAEPEncoding. Sending invalid ciphertext that decrypts to a short payload in the OAEP Decoder could result in the throwing of an early exception, potentially leaking some information about the private exponent of the RSA private key performing the encryption.

Record
GHSA-72m5-fvvv-55m6
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-203
Updated
2026-11-02
OSV 5.3

In Legion of the Bouncy Castle BC before 1.61 and BC-FJA before 1.0.1.2, attackers can obtain sensitive information about a private exponent because of Observable Differences in Behavior to Error Inputs. This occurs in org.bouncycastle.crypto.encodings.OAEPEncoding. Sending invalid ciphertext that decrypts to a short payload in the OAEP Decoder could result in the throwing of an early exception, potentially leaking some information about the private exponent of the RSA private key performing the encryption.

Record
CVE-2020-26939
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVDEBIAN-CVE-2020-26939 5.3

In Legion of the Bouncy Castle BC before 1.61 and BC-FJA before 1.0.1.2, attackers can obtain sensitive information about a private exponent because of Observable Differences in Behavior to Error Inputs. This occurs in org.bouncycastle.crypto.encodings.OAEPEncoding. Sending invalid ciphertext that decrypts to a short payload in the OAEP Decoder could result in the throwing of an early exception, potentially leaking some information about the private exponent of the RSA private key performing the encryption.

Record
DEBIAN-CVE-2020-26939
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVGHSA-72m5-fvvv-55m6 5.3

Observable Differences in Behavior to Error Inputs in Bouncy Castle

In Legion of the Bouncy Castle BC before 1.55 and BC-FJA before 1.0.2, attackers can obtain sensitive information about a private exponent because of Observable Differences in Behavior to Error Inputs. This occurs in org.bouncycastle.crypto.encodings.OAEPEncoding. Sending invalid ciphertext that decrypts to a short payload in the OAEP Decoder could result in the throwing of an early exception, potentially leaking some information about the private exponent of the RSA private key performing the encryption.

Record
GHSA-72m5-fvvv-55m6
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-203
Updated
2026-11-02
OSVUBUNTU-CVE-2020-26939 5.3

In Legion of the Bouncy Castle BC before 1.61 and BC-FJA before 1.0.1.2, attackers can obtain sensitive information about a private exponent because of Observable Differences in Behavior to Error Inputs. This occurs in org.bouncycastle.crypto.encodings.OAEPEncoding. Sending invalid ciphertext that decrypts to a short payload in the OAEP Decoder could result in the throwing of an early exception, potentially leaking some information about the private exponent of the RSA private key performing the encryption.

Record
UBUNTU-CVE-2020-26939
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
org.bouncycastle:bcprov-jdk14
Maven
before 1.61
1.61
org.bouncycastle:bcprov-jdk15
Maven
before 1.61
1.61
org.bouncycastle:bcprov-jdk16
Maven
before 1.61
1.61
org.bouncycastle:bc-fips
Maven
before 1.0.2
1.0.2
org.bouncycastle:bcprov-ext-jdk15on
Maven
before 1.61
1.61
org.bouncycastle:bcprov-ext-jdk16
Maven
before 1.61
1.61
org.bouncycastle:bcprov-jdk15on
Maven
before 1.61
1.61
org.bouncycastle:bcprov-jdk15to18
Maven
before 1.61
1.61
bouncycastle
Debian:12
before 1.61-1
1.61-1
bouncycastle
Debian:13
before 1.61-1
1.61-1
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Affected packages
PackageAffectedFixed
bouncycastle
Debian:14
before 1.61-1
1.61-1
bouncycastle
Debian:9
before 1.56-1+deb9u3, plus listed versions
1.56-11.56-1+deb9u11.56-1+deb9u2
1.56-1+deb9u3
org.bouncycastle:bcprov-jdk14
Maven
before 1.61, plus listed versions
1.381.431.441.451.46
Show 13 moreShow less
1.471.481.491.501.511.531.541.551.561.571.581.591.60
1.61
org.bouncycastle:bcprov-jdk15
Maven
before 1.61, plus listed versions
1.321.381.401.431.441.451.46
1.61
org.bouncycastle:bcprov-jdk16
Maven
before 1.61, plus listed versions
1.381.401.431.441.451.46
1.61
org.bouncycastle:bc-fips
Maven
before 1.0.2, plus listed versions
1.0.01.0.1
1.0.2
org.bouncycastle:bcprov-ext-jdk15on
Maven
before 1.61, plus listed versions
1.461.471.481.491.50
Show 10 moreShow less
1.511.521.531.541.551.561.571.581.591.60
1.61
org.bouncycastle:bcprov-ext-jdk16
Maven
before 1.61, plus listed versions
1.451.46
1.61
org.bouncycastle:bcprov-jdk15on
Maven
before 1.61, plus listed versions
1.461.471.481.491.50
Show 10 moreShow less
1.511.521.531.541.551.561.571.581.591.60
1.61
bouncycastle
Ubuntu:Pro:16.04:LTS
All versions, plus listed versions
1.49+dfsg-3ubuntu11.51-4ubuntu11.51-4ubuntu1+esm1
None known
bouncycastle
Ubuntu:Pro:18.04:LTS
All versions, plus listed versions
1.57-11.58-11.59-11.59-1ubuntu0.1~esm1
None known

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2020-26939 is a medium vulnerability (CVSS 5.3) in Bouncycastle Fips Java Api, published November 2, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.92%, the 60th percentile. Fixed in org.bouncycastle:bcprov-jdk14 1.61.

References

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