PT-2020-16386 · Tlslite Ng · Tlslite-Ng

Tomato42 · Published 2020-12-21 · Updated 2020-12-23 · CVE-2020-26263

Positive Technologies (AI Summary)

CVSS v4.0

8.7

High

Base vector

AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Name of the Vulnerable Software and Affected Versions tlslite-ng versions prior to 0.7.6 and 0.8.0-alpha39

Description The code that performs decryption and padding check in RSA PKCS#1 v1.5 decryption is data dependent, leaking information about the decrypted ciphertext. This affects all TLS servers that enable RSA key exchange and applications that use the RSA decryption API directly.

Recommendations For versions prior to 0.7.6, update to version 0.7.6 or later. For versions prior to 0.8.0-alpha39, update to version 0.8.0-alpha39 or later. As a temporary workaround, consider using different TLS implementations to minimize the risk of exploitation, as the patches depend on Python processing individual bytes in a side-channel free manner, which is known not to be the case.

Exploit

Fix

Inadequate Encryption Strength

Weakness Enumeration

CWE-326

Related Identifiers

CVE-2020-26263

GHSA-WVCV-832Q-FJG7

PYSEC-2020-143

Affected Products

Tlslite-Ng

References · 16

• 🔥 https://github.com/tlsfuzzer/tlslite-ng/security/advisories/GHSA-wvcv-832q-fjg7 · Exploit
• 🔥 https://securitypitfalls.wordpress.com/2018/08/03/constant-time-compare-in-python · Exploit
• https://github.com/tlsfuzzer/tlslite-ng/pull/439 · Patch
• https://github.com/tlsfuzzer/tlslite-ng/pull/438 · Patch
• https://github.com/tlsfuzzer/tlslite-ng/commit/c28d6d387bba59d8bd5cb3ba15edc42edf54b368 · Patch
• https://osv.dev/vulnerability/PYSEC-2020-143 · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2020-26263 · Vendor Advisory
• https://ubuntu.com/security/CVE-2020-26263 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2020-26263 · Security Note
• https://osv.dev/vulnerability/UBUNTU-CVE-2020-26263 · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2020-26263 · Security Note
• https://osv.dev/vulnerability/GHSA-wvcv-832q-fjg7 · Vendor Advisory
• https://github.com/pypa/advisory-database/tree/main/vulns/tlslite-ng/PYSEC-2020-143.yaml · Note
• https://github.com/tlsfuzzer/tlslite-ng · Note
• https://pypi.org/project/tlslite-ng · Note