CVE-2026-94300 ISC CVE debrief

Who should care

Defenders responsible for BIND 9 installations, especially those exposed to untrusted networks, should assess exposure and prioritize patching to prevent potential remote code execution.

Why it matters

CVE-2026-94300 is a memory corruption vulnerability in ISC BIND 9 that can lead to potential remote code execution. Defenders should prioritize patching BIND 9 installations, especially those exposed to untrusted networks, and verify affected versions.

• Potential remote code execution requires verification
• Memory corruption can lead to service disruption
• Defenders must verify affected versions and prioritize patching
• Exposure to untrusted networks increases risk

Technical summary

Replaying GSS-TSIG signed UDP messages can result in memory corruption in BIND 9. An attacker who can capture a previously signed UDP message can replay it while the negotiated TSIG key is still valid. By also sending crafted queries to a zone the attacker controls, the attacker may potentially achieve remote code execution. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.29, 9.21.0 through 9.21.26, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.29-S1. Defenders should prioritize patching BIND 9 installations, especially those exposed to untrusted networks, to prevent potential remote code execution.

Defensive priority

Defenders should prioritize patching BIND 9 installations, especially those exposed to untrusted networks, to prevent potential remote code execution.

Recommended defensive actions

• Patch BIND 9 installations to version 9.20.30 or later
• Patch BIND 9 installations to version 9.21.27 or later
• Restrict access to BIND 9 from untrusted networks
• Monitor BIND 9 logs for suspicious activity
• Verify affected BIND 9 versions and prioritize patching
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record and source item provide details on the vulnerability, but the scope of affected versions and potential impact require verification from official ISC sources. The vulnerability allows for potential remote code execution by replaying GSS-TSIG signed UDP messages, and defenders should verify affected versions and prioritize patching. Official sources such as the CVE Program and NIST NVD provide additional context.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.