HOMEVULNERABILITIESCVE-2020-26939
MEDIUM

CVE-2020-26939

CWE-203Published: November 2, 2020· Updated: Jun 17, 2026

5.3
CVSS v3.1

Official Description

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.

NVD Source

Technical Analysis

CVE-2020-26939 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityLow
IntegrityNone
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected Vendors & Products

bouncycastle2 product(s)
fips java apilegion-of-the-bouncy-castle
Source: NVD CPE · 2 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://github.com/bcgit/bc-java/wiki/CVE-2020-26939
PATCHhttps://github.com/bcgit/bc-java/wiki/CVE-2020-26939

All References (4)

→
https://github.com/bcgit/bc-java/wiki/CVE-2020-26939Patch · Third Party Advisory
→
https://lists.apache.org/thread.html/r8c36ba34e80e05eecb1f80071cc834d705616f315b634ec0c7d8f42e%40%3Cissues.solr.apache.org%3E
→
https://github.com/bcgit/bc-java/wiki/CVE-2020-26939Patch · Third Party Advisory
→
https://lists.apache.org/thread.html/r8c36ba34e80e05eecb1f80071cc834d705616f315b634ec0c7d8f42e%40%3Cissues.solr.apache.org%3E

Quick Facts

CVE IDCVE-2020-26939
CVSS Score5.3 / 10
SeverityMEDIUM
WeaknessCWE-203
CISA KEVNo
Affected1 vendor(s)
PublishedNov 2, 2020

Related CVEs (CWE-203)

CVE-2024-25189
9.8
CVE-2024-25190
9.8
CVE-2019-25337
9.8
CVE-2018-1000884
9.8
CVE-2024-23771
9.8
CVE-2024-25191
9.8

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2020-26939 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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