Vulnerability identifier: #VU48199

Vulnerability risk: Medium

CVSSv3.1: 4.6 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2020-26939

CWE-ID: CWE-200

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
The Bouncy Castle Crypto Package For Java
Universal components / Libraries / Libraries used by multiple products

Vendor: Legion of the Bouncy Castle Inc.

Description

The vulnerability allows a remote attacker to gain access to potentially sensitive information.

The vulnerability exists due to observable differences in behavior to error inputs within the org.bouncycastle.crypto.encodings.OAEPEncoding component in Legion of the Bouncy Castle BC. A remote attacker can obtain sensitive information about a private exponent by sending invalid ciphertext that decrypts to a short payload in the OAEP Decoder. This causes the application to throw an early exception, potentially leaking some information about the private exponent of the RSA private key performing the encryption.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

The Bouncy Castle Crypto Package For Java: 1.50 - 1.60

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External links
http://github.com/bcgit/bc-java/commit/930f8b274c4f1f3a46e68b5441f1e7fadb57e8c1
http://github.com/bcgit/bc-java/wiki/CVE-2020-26939
http://lists.debian.org/debian-lts-announce/2020/11/msg00007.html

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.