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TI-2025-27239 Aliases CVE-2025-40777GHSA-4x4c-8qp9-8ggh

A possible assertion failure when 'stale-answer-client-timeout' is set to '0'

Priority MEDIUM 41CWE-617Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-617.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.01016 63rd percentileScored 2026-11-07
Fix Fixed BIND 9 (ISC): 9.18.0, 9.18.11-S1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
ISCBIND 99.20.0 – 9.20.10; 9.21.0 – 9.21.9; 9.20.9-S1 – 9.20.10-S19.18.0, 9.18.11-S1Patch availableCNA
  • BIND 9 VendorISC Affected 9.20.0 – 9.20.10; 9.21.0 – 9.21.9; 9.20.9-S1 – 9.20.10-S1 Fixed in 9.18.0, 9.18.11-S1 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*——ISC
  • cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:* Versions — — ·ISC

Remediation

  • Fix · CNA BIND 9 (ISC) Fixed in 9.18.0, 9.18.11-S1

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Not affected: 6 products
  • Red Hat Enterprise Linux 10
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9
  • Red Hat OpenShift Container Platform 4

Timeline

  1. 2026-10-02 Threatist record created from CVE-2025-40777
  2. 2026-10-03 Alias added: GHSA-4x4c-8qp9-8ggh

References

Advisory 1

  • TI-2015-04610 Assertion failure in ISC BIND named via TKEY queries KEVCVSS 3.1HIGH 7.5
  • TI-2023-27571 Certain DNSSEC aspects of the DNS protocol (in RFC 4033, 4034, 4035, 6840, and related… CVSS 3.1HIGH 7.5
  • TI-2021-07476 A second vulnerability in BIND's GSSAPI security policy negotiation can be targeted by a buffer overflow attack CVSS 3.1CRITICAL 9.8
  • TI-1999-00042 Command execution via shell metachars in INN daemon (innd) 1.5 using "newgroup" and… CVSS 3.1CRITICAL 9.8
  • TI-2023-27773 The Closest Encloser Proof aspect of the DNS protocol (in RFC 5155 when RFC 9276 guidance… CVSS 3.1HIGH 7.5
  • TI-2025-27240 Cache poisoning attacks with unsolicited RRs CVSS 3.1HIGH 8.6
See all 285 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences