{"cve":"CVE-2020-26263","nvd":{"published":"2020-12-21T17:15:12.637","modified":"2026-06-17T03:07:57.120","status":"Modified","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_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","score":7.5},"cwes":["CWE-326"],"references":["https://github.com/tlsfuzzer/tlslite-ng/commit/c28d6d387bba59d8bd5cb3ba15edc42edf54b368","https://github.com/tlsfuzzer/tlslite-ng/pull/438","https://github.com/tlsfuzzer/tlslite-ng/pull/439","https://github.com/tlsfuzzer/tlslite-ng/security/advisories/GHSA-wvcv-832q-fjg7","https://pypi.org/project/tlslite-ng/"],"products":["tlslite-ng_project:tlslite-ng"],"source":"nvd","synced_at":"2026-10-19T21:12:09.559580076+00:00"},"epss":{"cve":"CVE-2020-26263","score":0.01523,"percentile":0.7463,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-wvcv-832q-fjg7","url":"https://osv.dev/vulnerability/GHSA-wvcv-832q-fjg7","summary":"RSA weakness in tslite-ng","modified":"2026-07-08T05:59:56.165718365Z","packages":[{"ecosystem":"PyPI","name":"tlslite-ng","purl":"pkg:pypi/tlslite-ng","ranges":["<0.7.6"],"fixed":["0.7.6"]}]},{"id":"PYSEC-2020-143","url":"https://osv.dev/vulnerability/PYSEC-2020-143","summary":"","modified":"2023-11-08T04:03:16.868623Z","packages":[{"ecosystem":"PyPI","name":"tlslite-ng","purl":"pkg:pypi/tlslite-ng","ranges":["<0.7.6"],"fixed":["0.7.6"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}