CVE-2026-70470: Flowise: Pyodide validator Unicode homoglyph bypass leads to RCE

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 1.0%, percentile 62: FIRST’s model estimates a 1.0% chance of exploitation activity in the next 30 days, higher than 62% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes flowise (npm) <= 3.1.2, fixed in 3.1.3; flowise-components (npm) <= 3.1.2, fixed in 3.1.3. Check your lockfile, including transitive dependencies.

What it is

Flowise is a drag & drop user interface to build a customized large language model flow. Prior to 3.1.3, Flowise validatePythonCodeForDataFrame in packages/components/src/pythonCodeValidator.ts can be bypassed with Unicode homoglyph identifiers, allowing arbitrary Python execution inside Pyodide and full OS command execution on the Flowise host via Pyodide js module interop. The validator gates pyodide.runPythonAsync in packages/components/nodes/agents/CSVAgent/CSVAgent.ts and packages/components/nodes/agents/AirtableAgent/AirtableAgent.ts with an ASCII word-boundary blacklist. JavaScript regex word boundaries are ASCII-only, while Python 3 NFKC-normalizes identifiers at parse time, so homoglyph forms such as cl𝐚ss, subcl𝐚sses, b𝐚se, and b𝐮iltins bypass the blacklist and are parsed as their ASCII equivalents. This issue is fixed in version 3.1.3.

From the GitHub advisory

Summary The validatePythonCodeForDataFrame blacklist in packages/components/src/pythonCodeValidator.ts can be bypassed with Unicode homoglyph identifiers, allowing arbitrary Python execution inside Pyodide and full OS command execution on the Flowise host via Pyodide's js module interop. This reopens the RCE paths patched as GHSA-3hjv-c53m-58jj (CSV Agent) and GHSA-v38x-c887-992f (Airtable Agent).

Details packages/components/src/pythonCodeValidator.ts gates every call to pyodide.runPythonAsync in packages/components/nodes/agents/CSVAgent/CSVAgent.ts (lines 147, 198) and packages/components/nodes/agents/AirtableAgent/AirtableAgent.ts (line 186). The gate is a regex blacklist:

Two design flaws combine into a bypass:

1. JavaScript regex \b is ASCII-only. Word boundaries are computed against the ASCII word class [A-Za-z0-9]. A Unicode letter such as U+1D41A (mathematical bold small a) is treated as a non-word character, so \bclass\b never matches cl𝐚ss. 2. Python 3 (PEP 3131) NFKC-normalizes every identifier at parse time. cl𝐚ss, subcl𝐚sses, b𝐚se, b𝐮iltins, and similar homoglyph forms are all parsed as their ASCII equivalents.

Attribute access obj.cl𝐚ss is normalized because attribute names are identifiers. Dict string keys such as bi['import'] are not normalized, but they are free text and can be assembled with chr() to avoid literal matches on patterns like \bimport\b or \bimport\s\(/.

Weakness type: CWE-184.

Product: flowise (npm) · Assigned by: GitHub_M · Published: 2026-08-04

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: high (needs special conditions)
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.97% probability of exploitation activity in the next 30 days; percentile 62.

Timeline

• 2026-08-04 — CVE record last updated
• 2026-08-04 — CVE record published by GitHub_M
• 2026-08-04 — GitHub-reviewed advisory GHSA-52fh-8v99-63c2 published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-52fh-8v99-63c2 github.com
2. CVE.org record CVE-2026-70470 cve.org
3. NVD entry CVE-2026-70470 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com

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