CVE-2020-26263RSA vulnerability in tslite-ng
- 7.5HighCVSS base score
- 1.5%Exploitation in 30 daysEPSS · top 25% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By GitHub_M
- 3 months later
· 3 months later
Published
- 4 years later
· 4 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
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 (13 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
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
References6
- 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)
- EUVD EUVD-2020-0221 (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://cveledger.app/cve/CVE-2020-26263)Record last updated .