CVE-2025-40777

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.

Affected Software

VendorProductVersion RangeStatus
ISCBIND 99.20.0 <= 9.20.10affected
ISCBIND 99.21.0 <= 9.21.9affected
ISCBIND 99.20.9-S1 <= 9.20.10-S1affected
ISCBIND 99.18.0 <= 9.18.37unaffected
ISCBIND 99.18.11-S1 <= 9.18.37-S1unaffected

Weaknesses

  • CWE-617: CWE-617 Reachable Assertion

Workarounds

Setting either of stale-answer-client-timeout off; or stale-answer-enable no; in the configuration file will prevent the assertion.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: yes
    • Technical Impact: partial

CVE Program Container

Additional References

References