libcurl TFTP State Machine Mis-Validation Enables Mixed-Mode TFTP Attack
CVE-2026-92389 Published on October 20, 2026

TFTP direction confusion
libcurl's TFTP state machine fails to validate state transitions against the requested transfer direction, accepting opening server responses for both reads and writes interchangeably. A malicious TFTP server can respond to a download request in a way that forces the client into transmit mode, prompting libcurl to consume and transmit data from the handle's persistent `CURLOPT_READDATA` pointer - including data remaining from unrelated prior operations, such as an HTTP POST request executed on a reused handle.

NVD

Vulnerability Analysis

CVE-2026-92389 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. Public availability of a proof of concept (POC) exploit exists for CVE-2026-92389. 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 Type

What is an Information Disclosure Vulnerability?

The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.

CVE-2026-92389 has been classified to as an Information Disclosure vulnerability or weakness.


Products Associated with CVE-2026-92389

stack.watch emails you whenever new vulnerabilities are published in Canonical Ubuntu Linux or Haxx Curl. Just hit a watch button to start following.

Canonical Ubuntu Linux
 
Haxx Curl
 

Affected Versions

curl: