National Vulnerability Database

National Vulnerability Database

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CVE-2020-26263 Detail

Current Description

tlslite-ng is an open source python library that implements SSL and TLS cryptographic protocols. In tlslite-ng before versions 0.7.6 and 0.8.0-alpha39, the code that performs decryption and padding check in RSA PKCS#1 v1.5 decryption is data dependant. In particular, the code has multiple ways in which it leaks information about the decrypted ciphertext. It aborts as soon as the plaintext doesn't start with 0x00, 0x02. All TLS servers that enable RSA key exchange as well as applications that use the RSA decryption API directly are vulnerable. This is patched in versions 0.7.6 and 0.8.0-alpha39. Note: the patches depend on Python processing the individual bytes in side-channel free manner, this is known to not the case (see reference). As such, users that require side-channel resistance are recommended to use different TLS implementations, as stated in the security policy of tlslite-ng.


View Analysis Description

Severity

 


CVSS 3.x Severity and Metrics:

NIST CVSS score
NIST: NVD
Base Score:  7.5 HIGH
Vector:  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Nist CVSS score does not match with CNA score
CNA:  GitHub, Inc.
Base Score:  7.5 HIGH
Vector:  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N


NVD Analysts use publicly available information to associate vector strings and CVSS scores. We also display any CVSS information provided within the CVE List from the CNA.

Note: It is possible that the NVD CVSS may not match that of the CNA. The most common reason for this is that publicly available information does not provide sufficient detail or that information simply was not available at the time the CVSS vector string was assigned.

References to Advisories, Solutions, and Tools

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Hyperlink Resource
https://github.com/tlsfuzzer/tlslite-ng/commit/c28d6d387bba59d8bd5cb3ba15edc42edf54b368 Patch  Third Party Advisory 
https://github.com/tlsfuzzer/tlslite-ng/pull/438 Patch  Third Party Advisory 
https://github.com/tlsfuzzer/tlslite-ng/pull/439 Patch  Third Party Advisory 
https://github.com/tlsfuzzer/tlslite-ng/security/advisories/GHSA-wvcv-832q-fjg7 Exploit  Patch  Third Party Advisory 
https://pypi.org/project/tlslite-ng/ Product  Third Party Advisory 
https://securitypitfalls.wordpress.com/2018/08/03/constant-time-compare-in-python/ Exploit  Third Party Advisory 

Weakness Enumeration

CWE-ID CWE Name Source
CWE-326 Inadequate Encryption Strength Provider acceptance level GitHub, Inc.  

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Change History

1 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2020-26263
NVD Published Date:
12/21/2020
NVD Last Modified:
12/23/2020
Source:
GitHub, Inc.