IBM Langflow OSS CVE-2026-77819

Requires an authenticated session on Langflow OSS (CVSS PR:L indicates a valid low-privileged account is needed - exploitation is not available to fully unauthenticated attackers). The flaw stems from improper limitation of a pathname to a restricted directory, so exploitation involves supplying a pathname that escapes the intended directory to write/overwrite files; the specific feature, endpoint, or parameter that accepts the pathname is not described in the available sources. Affected deployments are Langflow OSS versions 1.0.0 through 1.12.3. The primary limiting factor is the authentication requirement; the main aggravating factor is that the vector is network-reachable with low attack complexity and no user interaction, so any attacker who can obtain even a low-privileged account on a reachable instance can attempt it.

This is a moderate-severity, authenticated path traversal flaw (CWE-22) allowing arbitrary file overwrite in IBM Langflow OSS. The supplied CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N, base 6.5) indicates network-reachable, low-complexity exploitation that requires some level of authentication (PR:L) and yields a pure integrity impact with no confidentiality or availability loss stated. The vuln.today decision label is 'this_month', which signals a prioritized-but-not-emergency remediation timeline rather than immediate crisis response. No EPSS score was provided, the CVE is NOT listed in CISA KEV, and no PoC or exploit reference appears in the input - so there is no public exploit identified at time of analysis and no evidence of active exploitation. The practical risk tension is that arbitrary file overwrite is often a stepping stone to code execution or privilege escalation (overwriting configs, scripts, or startup files), which can be more dangerous than the I:H-only vector suggests; however, the input does not describe the trigger mechanism or any chaining, so that escalation potential is inferred, not confirmed. Net: a real priority to patch for anyone running Langflow with multi-user or exposed access, but the authentication requirement and absence of exploitation signals keep it below drop-everything urgency.

A remote attacker holding a valid low-privileged Langflow account sends a request containing a crafted pathname with directory-traversal sequences, causing the application to write or overwrite a file outside the intended restricted directory. By overwriting a configuration file, script, or application asset, the attacker could corrupt data or potentially stage follow-on code execution. No public PoC or exploit code is identified in the available sources, and the exact triggering endpoint/parameter is not described.