CVE-2020-26263 Information

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 PKCS1 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.

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Reference

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

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

NONE

Base Score

NONE

Base Severity

7.5