What is CVE-2026-12940?

CVE-2026-12940 is a critical-severity vulnerability in IBM Langflow Oss, classified under OS Command Injection. CVSS score: 9.8/10. Published 2026-07-30.

How severe is CVE-2026-12940?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2026-12940 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

RCE in IBM Langflow Oss

CVE-2026-12940

IBM Langflow OSS 1.0.0 through 1.10.1 are vulnerable to unauthenticated remote code execution via environment variable injection in the MCP (Model Context Protocol) stdio launcher. The vulnerability exists in src/lfx/src/lfx/base/mcp/util.py where the DANGEROUS_ENV_VARS blocklist fails to include SHELLOPTS , BASHOPTS , and PS4 environment variables.

Vulnerability class: Command Injection (OS Command Injection)

EPSS: 0.007 (50.6th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Ibm Langflow Oss — versions 1.0.0
Langflow

Weakness classification (CWE)

CWE-78 — OS Command Injection

Public proof-of-concept exploits

BiiTts/CVE-2026-12940-Langflow-Unauth-RCE

References

psirt@us.ibm.com (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-12940?: CVE-2026-12940 is a critical-severity vulnerability in IBM Langflow Oss, classified under OS Command Injection. CVSS score: 9.8/10. Published 2026-07-30.
How severe is CVE-2026-12940?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2026-12940 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.