CVE-2020-26263

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 1.3%, top 33% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this week
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
7.5
EG Score
7.5(medium)
EG Risk
39(Track)
EG Risk 39/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
66.9%
KEV
Not listed

Published

December 21, 2020

Last Modified

November 21, 2024

References (12)

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
tlslite-ng0.5.0-beta1 ... 0.7.5 (32 versions)0.7.6—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 45× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-23 01:51 UTCEG score recompute
  2. 2026-07-22 22:37 UTCEG score recompute
  3. 2026-07-22 14:05 UTCEPSS rescore
  4. 2026-07-21 15:22 UTCEPSS rescore
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  10. 2026-07-19 05:22 UTCOSV refresh
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  1. 2026-07-07 13:43 UTCEPSS rescore
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  8. 2026-07-01 11:46 UTCOSV refresh
  9. 2026-06-30 23:20 UTCEPSS rescore
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  35. 2026-06-13 19:13 UTCOSV refresh
  36. 2026-06-12 23:10 UTCEPSS rescore
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  63. 2026-05-27 13:39 UTCEPSS rescore
  64. 2026-05-26 23:09 UTCEG score recompute
  65. 2026-05-26 13:42 UTCEPSS rescore
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  69. 2026-05-24 16:48 UTCEPSS rescore
  70. 2026-05-23 09:31 UTCOSV refresh

Frequently asked(5)

What is CVE-2020-26263?
CVE-2020-26263 is a high vulnerability published on December 21, 2020. 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…
When was CVE-2020-26263 disclosed?
CVE-2020-26263 was first published in the National Vulnerability Database on December 21, 2020, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2020-26263 actively exploited?
CVE-2020-26263 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 66.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2020-26263?
CVE-2020-26263 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2020-26263?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2020-26263, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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