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CVE Record

CVE-2020-26939: In Legion of the Bouncy Castle BC before 1.61 and BC-FJA before 1.0.1.2, attackers can obtain sensitive inf...

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This flaw affects older Bouncy Castle cryptography libraries. When RSA OAEP decryption receives certain invalid ciphertext, the library may fail differently and too early, creating a side channel that could reveal information about the RSA private exponent.

Executive priority

Treat as a targeted cryptography dependency risk. Prioritize internet-facing or partner-facing services that decrypt external RSA OAEP ciphertext, then remediate bundled vulnerable Bouncy Castle versions through normal dependency and vendor update channels.

Technical view

CVE-2020-26939 is an observable-behavior issue in org.bouncycastle.crypto.encodings.OAEPEncoding in BC before 1.61 and BC-FJA before 1.0.1.2. Invalid ciphertext that decrypts to a short payload could trigger an early exception, potentially leaking private-exponent information from the RSA private key used for decryption.

Likely exposure

Exposure is most likely in Java applications or bundled products using vulnerable Bouncy Castle versions for RSA OAEP decryption of attacker-supplied ciphertext. The Apache Solr reference shows downstream concern about bundled Bouncy Castle, but the provided sources do not prove broad Solr exploitability.

Exploitation context

The source bundle does not show CISA KEV listing or active exploitation. The plausible attack context is repeated attacker-controlled invalid ciphertext reaching a vulnerable OAEP decoder and producing distinguishable behavior. Practical risk depends on whether application errors or timing differences are observable.

Researcher notes

Evidence is limited to version ranges and behavior summary. No CVSS, CWE, patch details, exploit proof, or KEV signal is provided. Avoid assuming exploitability unless a specific application exposes distinguishable OAEP decryption failures to an attacker.

Mitigation direction

  • Upgrade Bouncy Castle BC to 1.61 or later.
  • Upgrade BC-FJA to 1.0.1.2 or later.
  • Inventory applications and products bundling Bouncy Castle.
  • Check vendor advisories for downstream products that ship Bouncy Castle.
  • Limit exposure of RSA OAEP decryption endpoints to untrusted inputs.

Validation and detection

  • Identify Bouncy Castle library versions in dependency manifests and packaged artifacts.
  • Confirm whether org.bouncycastle.crypto.encodings.OAEPEncoding is used for RSA OAEP decryption.
  • Review public APIs that accept ciphertext from unauthenticated or external users.
  • Check whether applications disclose detailed decryption errors or timing differences.
  • Verify downstream vendor remediation for bundled Bouncy Castle components.
Prepared
Confidence
medium
Sources
4

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

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

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