Threat actors have begun exploiting a high-severity vulnerability in the popular low-code AI development platform Langflow, according to VulnCheck.
Tracked as CVE-2026-5027 (CVSS score of 8.8), the security defect is described as a path traversal issue that allows attackers to write files to arbitrary locations on the system.
“The ‘POST /api/v2/files’ endpoint does not sanitize the ‘filename’ parameter from the multipart form data, allowing an attacker to write files to arbitrary locations on the filesystem using path traversal sequences (‘../’),” a NIST advisory reads.
Successful exploitation of the bug, VulnCheck VP of security research Caitlin Condon warns, allows unauthenticated attackers to execute arbitrary code on vulnerable instances.
“The flaw can enable remote code execution (RCE), and because Langflow enables unauthenticated auto-login by default, attackers can reach the vulnerable endpoint without credentials,” VulnCheck told SecurityWeek.
Threat actors can send a single unauthenticated request to obtain a valid session token and then proceed to exploit CVE-2026-5027, it says.
According to VulnCheck, the observed in-the-wild exploitation attempts successfully leveraged the path traversal to drop test files on victim systems.
The potential attack surface appears broad, with approximately 7,000 Langflow instances accessible from the internet, most of them in North America.
“The activity underscores a growing trend of attackers targeting the infrastructure and tooling that organizations use to build and deploy AI applications,” VulnCheck said.
CVE-2026-5027 was disclosed publicly on March 27 by Tenable, after a series of failed disclosure attempts.
SecurityWeek has emailed Langflow for a statement and will update this article if it responds.
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