Cache poisoning due to weak PRNG

Description

In specific circumstances, due to a weakness in the Pseudo Random Number Generator (PRNG) that is used, it is possible for an attacker to predict the source port and query ID that BIND will use. This issue affects BIND 9 versions 9.16.0 through 9.16.50, 9.18.0 through 9.18.39, 9.20.0 through 9.20.13, 9.21.0 through 9.21.12, 9.16.8-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.39-S1, and 9.20.9-S1 through 9.20.13-S1.

Scores

EPSS (exploitation in 30 days)

0.47% · top 59% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: yes · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.6.

Weakness

• CWE-341 Predictable from Observable State (opens in a new tab)All about CWE-341 and its CVEs

Affected products

• ISC · BIND 9

  • affected 9.16.0 – ≤ 9.16.50
  • affected 9.18.0 – ≤ 9.18.39
  • affected 9.20.0 – ≤ 9.20.13
  • affected 9.21.0 – ≤ 9.21.12
  • affected 9.16.8-S1 – ≤ 9.16.50-S1
  • affected 9.18.11-S1 – ≤ 9.18.39-S1
  • affected 9.20.9-S1 – ≤ 9.20.13-S1

What to do

Solution: Upgrade to the patched release most closely related to your current version of BIND 9: 9.18.41, 9.20.15, 9.21.14, 9.18.41-S1, or 9.20.15-S1.

Workaround: No workarounds known.

Exploitation: We are not aware of any active exploits.

References (2)

• CVE-2025-40780 (opens in a new tab)vendor-advisory
• http://www.openwall.com/lists/oss-security/2025/10/22/1 (opens in a new tab)

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)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2025-40780](https://trackcve.app/badge/CVE-2025-40780.svg)](https://trackcve.app/cve/CVE-2025-40780)

Record last updated 4 Nov 2025, 21:10 UTC.