CVE-2020-26263 RSA vulnerability in tslite-ng
Attackers can exploit timing side-channels in RSA decryption to leak plaintext information, affecting TLS servers and applications using tlslite-ng.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2020-26263?
CVE-2020-26263 is a high-severity vulnerability in tlsfuzzer tlslite-ng, published on 21 Dec 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-326
Which versions are affected by CVE-2020-26263?
3 open source packages ship an affected version, including tlslite-ng. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
tlslite-ng PyPI | All versions | 0.7.6 |
tlslite-ng PyPI | All versions | 0.7.6 |
tlslite-ng PyPI | All versions | 0.7.6 |
Products include Tlslite-Ng Project Tlslite-Ng.
How do I fix CVE-2020-26263?
Upgrade tlslite-ng to 0.7.6 or later.
Is CVE-2020-26263 being exploited?
There is no known exploitation of CVE-2020-26263 in the wild and no public exploit code.
Other vulnerabilities in tlsfuzzer tlslite-ng
Sources
Also known as GHSA-wvcv-832q-fjg7, PYSEC-2020-143, UBUNTU-CVE-2020-26263.