CyberSecBulletin
CVE-2023-4236NVD status: Modified

BIND 9: Reachable Assertion

Published Updated By the CyberSecBulletin desk

CVE-2023-4236 is a high-severity reachable assertion vulnerability in BIND 9 from ISC, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected BIND 9 versions: 9.18.0 through 9.18.18; 9.18.11-S1 through 9.18.18-S1. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 2.19% chance of exploitation within 30 days, higher than 83% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Bind to 9.18.18 or a later version.
  2. Read the advisory on kb.isc.org for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
ISCBIND 99.18.0 through 9.18.18; 9.18.11-S1 through 9.18.18-S1Not stated
ISCBind9.18.0 up to, but not including, 9.18.18; 9.18.11; 9.18.189.18.18
Fedora ProjectFedora37; 38; 39Not stated
DebianDebian Linux10.0; 11.0Not stated
NetAppH300s FirmwareNot specified in the recordNot stated
NetAppH500s FirmwareNot specified in the recordNot stated
NetAppH700s FirmwareNot specified in the recordNot stated
NetAppH410s FirmwareNot specified in the recordNot stated
NetAppH410c FirmwareNot specified in the recordNot stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA (isc.org).

Official description

A flaw in the networking code handling DNS-over-TLS queries may cause `named` to terminate unexpectedly due to an assertion failure. This happens when internal data structures are incorrectly reused under significant DNS-over-TLS query load. This issue affects BIND 9 versions 9.18.0 through 9.18.18 and 9.18.11-S1 through 9.18.18-S1.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Reachable Assertion

The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.

How developers prevent this class of flaw

  • If the assertion statement is required (e.g., for security or reliability), change the invoking code to avoid the conditions that trigger the assertion.
  • Consider changing the assertion to some other less fatal error. This might not be easy to implement, since other code may be needed to handle the error.
  • Make sensitive open/close operations non-reachable from directly user-controlled data (e.g. open/close resources)

More Reachable Assertion vulnerabilities (CWE-617)

Timeline

  1. CVE record published.
  2. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Other vulnerabilities in BIND 9

All BIND 9 vulnerabilities

Recent Reachable Assertion vulnerabilities

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