critical Threat analysis

Langflow CVE-2025-34291: KEV Origin Validation Exposure

CISA added Langflow CVE-2025-34291 to KEV on 2026-05-21. The issue combines permissive CORS and credentialed refresh-token behavior; this article provides dependency, container, HTTP telemetry, and token-abuse audit scripts.

Published: 2026-05-26
Read time: 6 min read
Sources: 4

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Executive Summary

CISA added CVE-2025-34291 to KEV on 2026-05-21 with a due date of 2026-06-04 CISA KEV. CISA describes an origin validation error where permissive CORS and a refresh token cookie configured as SameSite=None allow credentialed cross-origin refresh endpoint requests, enabling authenticated follow-on actions CISA KEV.

NVD lists vulnerable Langflow CPE entries through 1.6.9, while the vendor release reference in CISA KEV points to v1.9.3 NVD, Langflow release.

Key Facts

cve: "CVE-2025-34291"
vendor: "Langflow"
product: "Langflow"
kev_added: "2026-05-21"
kev_due: "2026-06-04"
vulnerability: "Origin validation error with credentialed cross-origin refresh-token requests"
cwe: ["CWE-346"]
nvd_vulnerable_cpe: "cpe:2.3:a:langflow:langflow:*:*:*:*:*:*:*:*"
nvd_vulnerable_version_end_including: "1.6.9"
vendor_reference_release: "v1.9.3"
cvss_v31: "8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
cvss_v40_secondary: "9.4 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H"
exploitation_status: "cisa_kev_exploited"
zero_day_status: "unproven_from_public_primary_sources"

Source Confidence & Evidence Mapping

confirmed: CISA KEV lists CVE-2025-34291 as known exploited and describes the CORS plus refresh-token failure mode CISA KEV.
confirmed: NVD lists CWE-346, CVSS 3.1 score 8.8, and vulnerable CPE through 1.6.9 NVD.
confirmed: CISA KEV references Langflow v1.9.3 and GitHub issue 11465 as vendor context Langflow release, Langflow issue.
unclear: Public primary sources do not provide a single stable refresh endpoint path or a complete list of exploited IPs.

Impact Determination

Classification	Criteria	Required evidence	Remediation trigger	Closure condition
Confirmed compromise	HTTP or application telemetry shows credentialed cross-origin refresh behavior followed by authenticated Langflow API activity on a vulnerable deployment.	Version evidence, Origin/Cookie/refresh telemetry, session or token activity, and affected host identity.	Preserve Langflow app logs, reverse-proxy logs, deployment manifests, and secrets available to the Langflow process.	Version is fixed or removed and downstream token/API audit shows no unexplained authenticated activity.
Presumed exposed	Langflow version is `<= 1.6.9` by NVD CPE or below vendor reference release 1.9.3 with browser-reachable deployment.	Lockfile, package inventory, container tag, scanner row, or runtime package output.	Keep the deployment in scope until version closure succeeds.	Script output proves version is outside the NVD vulnerable range and at or above the vendor reference release used for closure.
Potentially exposed	Langflow appears in source, images, manifests, or scanner exports but version or browser exposure is unknown.	Repository, image, Kubernetes, CMDB, or scanner evidence naming `langflow`.	Collect runtime version and exposure evidence.	Asset resolves to confirmed compromise, presumed exposed, not exposed, or unknown.
Not exposed	No Langflow package, image, deployment, scanner row, or CVE-2025-34291 selector appears in complete exports.	Negative outputs from repository, image, Kubernetes, and scanner collection.	None for this CVE.	Evidence bundle covers source, build artifacts, containers, and deployed workloads.
Unknown	Runtime version, exposure, or HTTP telemetry is unavailable.	Gap statement naming the unavailable source.	Keep externally reachable Langflow deployments in scope.	Evidence is recovered or the risk owner accepts the named gap.

Timeline

2025-12-05: NVD publication timestamp for CVE-2025-34291 NVD.
2026-05-21: CISA adds CVE-2025-34291 to KEV with due date 2026-06-04 CISA KEV.
2026-05-21: CISA KEV catalog points defenders to Langflow v1.9.3 and issue 11465 Langflow release.

What Happened

The exploitable condition is credentialed cross-origin access to Langflow refresh behavior, not a package compromise. The practical scoping anchors are langflow package versions, container images, exposed Langflow services, and HTTP telemetry containing Origin, credential cookies, and refresh-token activity.

Technical Analysis

Langflow deployments often hold model-provider credentials, workflow secrets, and API tokens. A successful refresh-token abuse path can convert a browser interaction into authenticated Langflow API access. The scripts below classify dependencies, containers, and HTTP telemetry without assuming a vendor route that public primary sources do not provide.

Affected Assets and Blast Radius

asset_selectors:
  - "langflow"
  - "CVE-2025-34291"
  - "CWE-346"
  - "v1.9.3"
version_selectors:
  nvd_vulnerable_end_including: "1.6.9"
  vendor_reference_release: "1.9.3"
credentials_and_data_at_risk:
  - "Langflow refresh tokens"
  - "authenticated Langflow API tokens"
  - "model provider secrets available to Langflow"
  - "workflow execution credentials"

Indicators And Detection Selectors

cves: ["CVE-2025-34291"]
packages: ["langflow"]
fixed_or_reference_versions: ["1.9.3"]
http_selectors:
  - "Origin"
  - "Cookie"
  - "SameSite=None"
  - "refresh token"
  - "refresh_token"
  - "Langflow"

Detection and Hunting

#!/usr/bin/env python3
import json
import os
import re
import sys
from pathlib import Path

ROOT = Path(os.environ.get("ROOT", sys.argv[1] if len(sys.argv) > 1 else ".")).resolve()
TELEMETRY_DIR = Path(os.environ.get("TELEMETRY_DIR", "telemetry-export")).resolve()
OUT = Path(os.environ.get("OUT", "hp-langflow-cve-2025-34291-scope")).resolve()
CVE = "CVE-2025-34291"
NVD_VULN_END = "1.6.9"
REFERENCE_RELEASE = "1.9.3"
SELECTORS = [CVE, "langflow", "Langflow", "CWE-346", "SameSite=None", "refresh token", "refresh_token", "Origin", "Cookie"]

def vt(value):
    return tuple(int(x) for x in re.findall(r"\d+", str(value))[:4])

def le(left, right):
    l, r = vt(left), vt(right)
    width = max(len(l), len(r), 1)
    return l + (0,) * (width - len(l)) <= r + (0,) * (width - len(r))

def lt(left, right):
    l, r = vt(left), vt(right)
    width = max(len(l), len(r), 1)
    return l + (0,) * (width - len(l)) < r + (0,) * (width - len(r))

def read_text(path):
    try:
        return path.read_text(encoding="utf-8", errors="ignore")
    except Exception:
        return ""

OUT.mkdir(parents=True, exist_ok=True)
results = {"dependency_hits": [], "container_or_manifest_hits": [], "http_telemetry_hits": []}
version_patterns = [
    re.compile(r"^\s*langflow\s*==\s*([0-9][0-9A-Za-z.\-+]*)", re.I | re.M),
    re.compile(r'name\s*=\s*"langflow".{0,200}?version\s*=\s*"([^"]+)"', re.I | re.S),
    re.compile(r"langflow[:=@\\s-]+v?([0-9]+\.[0-9]+\.[0-9]+)", re.I),
]

for path in list(ROOT.rglob("requirements*.txt")) + list(ROOT.rglob("pyproject.toml")) + list(ROOT.rglob("poetry.lock")) + list(ROOT.rglob("uv.lock")):
    if any(part in {".git", "node_modules", ".venv", "dist"} for part in path.parts):
        continue
    body = read_text(path)
    if "langflow" not in body.lower():
        continue
    versions = sorted({m.group(1).lstrip("v") for p in version_patterns for m in p.finditer(body)})
    results["dependency_hits"].append({
        "file": str(path),
        "package": "langflow",
        "versions": versions,
        "cve": CVE,
        "nvd_vulnerable_versions": [v for v in versions if le(v, NVD_VULN_END)],
        "below_reference_release": [v for v in versions if lt(v, REFERENCE_RELEASE)],
    })

for path in list(ROOT.rglob("Dockerfile*")) + list(ROOT.rglob("*.yaml")) + list(ROOT.rglob("*.yml")) + list(ROOT.rglob("*.json")):
    body = read_text(path)
    if "langflow" in body.lower() or CVE in body:
        results["container_or_manifest_hits"].append({"file": str(path), "selector": "langflow-or-cve"})

if TELEMETRY_DIR.exists():
    for path in TELEMETRY_DIR.rglob("*"):
        if path.is_file():
            for line_no, line in enumerate(read_text(path).splitlines(), start=1):
                if ("langflow" in line.lower() or CVE in line) and ("Origin" in line or "Cookie" in line or "refresh" in line.lower()):
                    results["http_telemetry_hits"].append({"file": str(path), "line": line_no, "evidence": line[:1000]})

(OUT / "langflow-cve-2025-34291-scope.json").write_text(json.dumps(results, indent=2, sort_keys=True), encoding="utf-8")

# Positive signal: langflow <= 1.6.9, langflow below 1.9.3, or HTTP telemetry containing Langflow plus Origin/Cookie/refresh selectors.
print(json.dumps({"out": str(OUT), "dependency_hits": len(results["dependency_hits"]), "http_hits": len(results["http_telemetry_hits"])}, indent=2))

Patch, Mitigation, and Verification

#!/usr/bin/env python3
import json
import os
import re
import subprocess
from pathlib import Path

OUT = Path(os.environ.get("OUT", "hp-langflow-cve-2025-34291-closure")).resolve()
CVE = "CVE-2025-34291"
NVD_VULN_END = "1.6.9"
REFERENCE_RELEASE = "1.9.3"
SOURCE = "https://github.com/langflow-ai/langflow/releases/tag/v1.9.3"

def vt(value):
    return tuple(int(x) for x in re.findall(r"\d+", str(value))[:4])

def ge(left, right):
    l, r = vt(left), vt(right)
    width = max(len(l), len(r), 1)
    return l + (0,) * (width - len(l)) >= r + (0,) * (width - len(r))

OUT.mkdir(parents=True, exist_ok=True)
result = {"cve": CVE, "reference_release": REFERENCE_RELEASE, "source": SOURCE, "python_runtime": [], "docker_images": []}

pip_cmds = [["python3", "-m", "pip", "show", "langflow"], ["python", "-m", "pip", "show", "langflow"]]
for cmd in pip_cmds:
    try:
        proc = subprocess.run(cmd, text=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, timeout=20)
    except Exception as exc:
        result["python_runtime"].append({"cmd": cmd, "error": str(exc)})
        continue
    version = ""
    for line in proc.stdout.splitlines():
        if line.lower().startswith("version:"):
            version = line.split(":", 1)[1].strip()
    if version:
        result["python_runtime"].append({
            "cmd": cmd,
            "installed_version": version,
            "nvd_vulnerable_end_including": NVD_VULN_END,
            "vendor_reference_release": REFERENCE_RELEASE,
            "at_or_above_reference_release": ge(version, REFERENCE_RELEASE),
        })

try:
    proc = subprocess.run(["docker", "images", "--format", "{{.Repository}}:{{.Tag}} {{.ID}}"], text=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, timeout=30)
    for line in proc.stdout.splitlines():
        if "langflow" in line.lower():
            result["docker_images"].append({"image": line, "selector": "langflow"})
except Exception as exc:
    result["docker_error"] = str(exc)

(OUT / "langflow-cve-2025-34291-version-verification.json").write_text(json.dumps(result, indent=2, sort_keys=True), encoding="utf-8")

# Remediation trigger: any runtime or image below Langflow 1.9.3, especially versions <= 1.6.9, remains open for CVE-2025-34291.
print(json.dumps({"out": str(OUT), "runtime_checks": len(result["python_runtime"]), "docker_hits": len(result["docker_images"])}, indent=2))

Downstream Abuse Audits

#!/usr/bin/env python3
import json
import os
import sys
from pathlib import Path

TELEMETRY_DIR = Path(os.environ.get("TELEMETRY_DIR", sys.argv[1] if len(sys.argv) > 1 else "telemetry-export")).resolve()
OUT = Path(os.environ.get("OUT", "hp-langflow-cve-2025-34291-downstream")).resolve()
CVE = "CVE-2025-34291"
SELECTORS = [
    "CVE-2025-34291",
    "langflow",
    "Langflow",
    "refresh_token",
    "refresh token",
    "OPENAI_API_KEY",
    "ANTHROPIC_API_KEY",
    "AZURE_OPENAI_API_KEY",
    "GOOGLE_API_KEY",
    "LANGFLOW_SECRET_KEY",
    "SameSite=None",
    "Origin",
]

if not TELEMETRY_DIR.exists():
    raise SystemExit(f"TELEMETRY_DIR not found: {TELEMETRY_DIR}")

OUT.mkdir(parents=True, exist_ok=True)
matches = []
for path in TELEMETRY_DIR.rglob("*"):
    if not path.is_file():
        continue
    for line_no, line in enumerate(path.read_text(encoding="utf-8", errors="ignore").splitlines(), start=1):
        for selector in SELECTORS:
            if selector in line:
                matches.append({"cve": CVE, "file": str(path), "line": line_no, "selector": selector, "evidence": line[:1000]})

(OUT / "langflow-cve-2025-34291-downstream-selectors.json").write_text(json.dumps(matches, indent=2, sort_keys=True), encoding="utf-8")

# Positive signal: post-exposure Langflow refresh activity, model-provider key exposure, or authenticated API activity tied to a vulnerable deployment.
# Remediation trigger: any Langflow token or provider key selector after the first vulnerable exposure keeps Langflow secrets and connected services in scope.
print(json.dumps({"out": str(OUT), "matches": len(matches)}, indent=2))