Vulnerability 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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Tlslite-Ng Project | Tlslite-Ng | < 0.7.6 |
Related Weaknesses (CWE)
References
- https://github.com/tlsfuzzer/tlslite-ng/commit/c28d6d387bba59d8bd5cb3ba15edc42edPatchThird Party Advisory
- https://github.com/tlsfuzzer/tlslite-ng/pull/438PatchThird Party Advisory
- https://github.com/tlsfuzzer/tlslite-ng/pull/439PatchThird Party Advisory
- https://github.com/tlsfuzzer/tlslite-ng/security/advisories/GHSA-wvcv-832q-fjg7ExploitPatchThird Party Advisory
- https://pypi.org/project/tlslite-ng/ProductThird Party Advisory
- https://securitypitfalls.wordpress.com/2018/08/03/constant-time-compare-in-pythoExploitThird Party Advisory
- https://github.com/tlsfuzzer/tlslite-ng/commit/c28d6d387bba59d8bd5cb3ba15edc42edPatchThird Party Advisory
- https://github.com/tlsfuzzer/tlslite-ng/pull/438PatchThird Party Advisory
- https://github.com/tlsfuzzer/tlslite-ng/pull/439PatchThird Party Advisory
- https://github.com/tlsfuzzer/tlslite-ng/security/advisories/GHSA-wvcv-832q-fjg7ExploitPatchThird Party Advisory
- https://pypi.org/project/tlslite-ng/ProductThird Party Advisory
- https://securitypitfalls.wordpress.com/2018/08/03/constant-time-compare-in-pythoExploitThird Party Advisory
FAQ
What is CVE-2020-26263?
CVE-2020-26263 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 ch...
How severe is CVE-2020-26263?
CVE-2020-26263 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2020-26263?
Check the references section above for vendor advisories and patch information. Affected products include: Tlslite-Ng Project Tlslite-Ng.