BIND 9 named GSS-TSIG Replay Causing Memory Corruption <9.18.50,9.21.26>
CVE-2026-94300 Published on October 21, 2026

Concurrent GSS-TSIG messages corrupt memory
Replaying GSS-TSIG signed UDP messages can result in memory corruption in "`named`". 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.

Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-94300 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.

Attack Vector:
NETWORK
Attack Complexity:
HIGH
Privileges Required:
NONE
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
HIGH

Weakness Types

What is a Double-free Vulnerability?

The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations. When a program calls free() twice with the same argument, the program's memory management data structures become corrupted. This corruption can cause the program to crash or, in some circumstances, cause two later calls to malloc() to return the same pointer. If malloc() returns the same value twice and the program later gives the attacker control over the data that is written into this doubly-allocated memory, the program becomes vulnerable to a buffer overflow attack.

CVE-2026-94300 has been classified to as a Double-free vulnerability or weakness.

What is a Race Condition Vulnerability?

The program contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.

CVE-2026-94300 has been classified to as a Race Condition vulnerability or weakness.


Products Associated with CVE-2026-94300

Want to know whenever a new CVE is published for ISC BIND? stack.watch will email you.

ISC BIND
 

Affected Versions

ISC BIND 9: