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Vulnerability record · CVE-2020-5929 · published 25 September 2020

CVE-2020-5929: F5 big-ip access policy manager observable discrepancy vulnerability

F5 · Big Ip Access Policy Manager

In versions 13.0.0-13.0.0 HF2, 12.1.0-12.1.2 HF1, and 11.6.1-11.6.2, BIG-IP platforms with Cavium Nitrox SSL hardware acceleration cards, a Virtual Server configured with a Client SSL profile, and using Anonymous (ADH) or Ephemeral (DHE) Diffie-Hellman key exchange and Single DH use option not enabled in the options list may be vulnerable to crafted SSL/TLS Handshakes that may result with a PMS (Pre-Master Secret) that starts in a 0 byte and may lead to a recovery of plaintext messages as BIG-IP TLS/SSL ADH/DHE sends different error messages acting as an oracle. Similar error messages when PMS starts with 0 byte coupled with very precise timing measurement observation may also expose this vulnerability.

5.9 CVSS 3.1 Medium EPSS 1.1% · top 35.9% CWE-203 · Observable discrepancy
5.9CVSS 3.1 base score, v2 2.6
1.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
14Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

Description

In versions 13.0.0-13.0.0 HF2, 12.1.0-12.1.2 HF1, and 11.6.1-11.6.2, BIG-IP platforms with Cavium Nitrox SSL hardware acceleration cards, a Virtual Server configured with a Client SSL profile, and using Anonymous (ADH) or Ephemeral (DHE) Diffie-Hellman key exchange and Single DH use option not enabled in the options list may be vulnerable to crafted SSL/TLS Handshakes that may result with a PMS (Pre-Master Secret) that starts in a 0 byte and may lead to a recovery of plaintext messages as BIG-IP TLS/SSL ADH/DHE sends different error messages acting as an oracle. Similar error messages when PMS starts with 0 byte coupled with very precise timing measurement observation may also expose this vulnerability.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

14 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://support.f5.com/csp/article/K91158923 Vendor Advisory
https://support.f5.com/csp/article/K91158923 Vendor Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2020-5929), CISA KEV, FIRST EPSS (scores of 2026-10-02). This page is refreshed as NVD updates the record.