7.5

CVE-2020-26263: RSA vulnerability in tslite-ng

Modified
AliasesGHSA-wvcv-832q-fjg7PYSEC-2020-143UBUNTU-CVE-2020-26263
Published 21-12-2020Last modified 04-08-2024

Vulnerability summary

CVE-2020-26263 is a high (CVSS 7.5) Inadequate Encryption Strength vulnerability in tlsfuzzer tlslite-ng. EPSS estimates a 1.52% chance of exploitation in the next 30 days, higher than 74.6% of scored vulnerabilities. 2 public exploits are recorded.

Priority
Prioritisepublic exploit

Public exploit (GitHub, Date unknown)

Source freshness unavailable

How is this decided?
CVSS score
7.5/10
010
High · v3.1 (CVE.org)
EPSS score
1.52%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits2github, reference

Timeline

  1. 21-12-2020
    PublishedVulnerability first disclosed.
  2. 04-08-2024
    Last modifiedVulnerability information updated.

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 metrics

6 scores · 4 sources · 3 versions

EPSS trend

Probability

1.52%

Chance of exploitation in the next 30 days

Percentile

75%

Versus all other CVEs

30-day change

No change 0.00 pp

From 1.52% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

2 found
  • githubUnverified

    Tlslite Ng

    Maturity: poc

  • referenceUnverified

    Exploit Reference (securitypitfalls.wordpress.com)

    Maturity: unknown

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

PyPI1 product
  • tlslite-ng< c28d6d387bba59d8bd5cb3ba15edc42edf54b368 | < 0.7.6
Tlsfuzzer1 product
  • tlslite-ng< 0.7.6 | ≥ 0.8.0-alpha1, < 0.8.0-alpha39
Tlslite-ng_project1 product
  • tlslite-ng< 0.7.6 | 0.8.0:alpha1 | 0.8.0:alpha10 | 0.8.0:alpha11 | 0.8.0:alpha12 | 0.8.0:alpha13 | 0.8.0:alpha14 | 0.8.0:alpha15 | 0.8.0:alpha16 | 0.8.0:alpha17 | 0.8.0:alpha18 | 0.8.0:alpha19 | 0.8.0:alpha2 | 0.8.0:alpha20 | 0.8.0:alpha21 | 0.8.0:alpha22 | 0.8.0:alpha23 | 0.8.0:alpha24 | 0.8.0:alpha25 | 0.8.0:alpha26 | 0.8.0:alpha27 | 0.8.0:alpha28 | 0.8.0:alpha29 | 0.8.0:alpha3 | 0.8.0:alpha30 | 0.8.0:alpha31 | 0.8.0:alpha32 | 0.8.0:alpha33 | 0.8.0:alpha34 | 0.8.0:alpha35 | 0.8.0:alpha36 | 0.8.0:alpha37 | 0.8.0:alpha38 | 0.8.0:alpha4 | 0.8.0:alpha5 | 0.8.0:alpha6 | 0.8.0:alpha7 | 0.8.0:alpha8 | 0.8.0:alpha9
Ubuntu1 product
  • tlslite-ngAll versions (No fix recorded)

4 vendors · 4 products

References

13 links
Show all 13 references