7.5

CVE-2025-40777: isc bind 9 Reachable Assertion

CVSS: 7.5v3.1HighDeferred
AliasesALPINE-CVE-2025-40777SUSE-SU-2025:02349-1UBUNTU-CVE-2025-40777
Published 16-07-2025Last modified 04-11-2025
Open JSON

Vulnerability summary

CVE-2025-40777 is a high (CVSS 7.5) Reachable Assertion vulnerability in isc bind 9. EPSS estimates a 1.03% chance of exploitation in the next 30 days, higher than 62.9% of scored vulnerabilities.

Overall risk
30/100
0100
Medium · default modelHow is this calculated?
CVSS score
7.5/10
010
High · v3.1 (CVE.org)
EPSS score
1.03%
0%100%
Low · +0.11 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 0 · Related 2
CGA-JHR7-46J2-MG2CCGA-M3R3-PGGV-4XPQ

Timeline

  1. 16-07-2025
    PublishedVulnerability first disclosed.
  2. 04-11-2025
    Last modifiedVulnerability information updated.

Description

If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable value other than `disabled`), and if the resolver, in the process of resolving a query, encounters a CNAME chain involving a specific combination of cached or authoritative records, the daemon will abort with an assertion failure. This issue affects BIND 9 versions 9.20.0 through 9.20.10, 9.21.0 through 9.21.9, and 9.20.9-S1 through 9.20.10-S1.

CVSS metrics

7 scores · 7 sources · 1 version

EPSS trend

Probability

1.03%

Chance of exploitation in the next 30 days

Percentile

63%

Versus all other CVEs

30-day change

+0.11 pp

From 0.92% on 18-09-2026

18-09-202618-10-2026
EPSS score
1.03%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Suse2 products
  • bind&distro=SUSE Linux Enterprise Module for Basesystem 15 SP7< 9.20.11-150700.3.6.1
  • bind&distro=SUSE Linux Enterprise Module for Server Applications 15 SP7< 9.20.11-150700.3.6.1
Alpine1 product
  • bind< 9.20.11-r0
Chainguard1 product
  • bind-dnssec-rootAll versions (No fix recorded)
Debian1 product
  • bind9All versions (No fix recorded) | < 1:9.20.11-1
Isc1 product
  • bind 9≥ 9.20.0, ≤ 9.20.10 | ≥ 9.21.0, ≤ 9.21.9 | ≥ 9.20.9-S1, ≤ 9.20.10-S1
Opensuse1 product
  • bind&distro=openSUSE Tumbleweed< 9.20.11-1.1
Ubuntu1 product
  • bind9< 1:9.20.4-3ubuntu1.2
Wolfi1 product
  • bind-dnssec-rootAll versions (No fix recorded)

8 vendors · 9 products

References

11 links
Show all 11 references