CVE-2020-26263
RSA vulnerability in tslite-ng
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
| NVDNVD · Modified | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
- EPSS (exploitation in 30 days)
- 1.5% · top 25% of all CVEs (7 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Weakness
Affected products
- affected < 0.7.6
- affected >= 0.8.0-alpha1, < 0.8.0-alpha39
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- PyPItlslite-ngGHSA-wvcv-832q-fjg7 (opens in a new tab)
References (6)
- https://github.com/tlsfuzzer/tlslite-ng/security/advisories/GHSA-wvcv-832q-fjg7 (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://securitypitfalls.wordpress.com/2018/08/03/constant-time-compare-in-python/ (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/tlsfuzzer/tlslite-ng/pull/438 (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/tlsfuzzer/tlslite-ng/pull/439 (opens in a new tab)x_refsource_MISCx_transferred
- https://pypi.org/project/tlslite-ng/ (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/tlsfuzzer/tlslite-ng/commit/c28d6d387bba59d8bd5cb3ba15edc42edf54b368 (opens in a new tab)x_refsource_MISCx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-wvcv-832q-fjg7 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2020-26263)Record last updated .