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Flyto Core EUVDEUVD-2026-58242

| CVE-2026-73530 MEDIUM
Server-Side Request Forgery (SSRF) (CWE-918)
2026-08-13 VulnCheck GHSA-35jm-rm2f-hpgj
6.3
CVSS 4.0 · Vendor: VulnCheck
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Authenticate with low-privilege credentials
  2. Delivery
    Supply crafted URL containing `::` (or trigger 302 redirect to `::`)
  3. Exploit
    URL bypasses is_private_ip() guard check
  4. Execution
    Flyto Core HTTP module issues request to IPv6 loopback
  5. Impact
    Internal service returns sensitive response to attacker

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V4 - API and Web Service URL allowlisting, SSRF prevention
MITRE ATT&CK

2 techniques across 2 tactics: Initial Access, Credential Access

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Exploitation requires authenticated access with at least low-privilege credentials to the Flyto Core application, as reflected in CVSS PR:L. The attacker must be able to supply or influence a URL processed by one of three specific HTTP modules: http.get, http.request, or http.batch. The bypass is reachable either by directly supplying a URL containing the IPv6 unspecified address :: (or expanded equivalents) or by controlling an intermediate server that returns a 302 redirect to such a URL, which means open-redirect vulnerabilities in third-party services reachable from Flyto Core could also be chained. Exploitation is limited to reaching services that are bound to the IPv6 loopback interface on the host running Flyto Core; services bound only to IPv4 loopback (127.0.0.1) or unreachable on IPv6 loopback are not directly exposed by this specific bypass. Deployments where all HTTP module inputs are fully system-controlled (no user-supplied URLs accepted) are not practically exploitable even on unpatched versions.

Impact

The CVSS 4.0 score of 6.3 reflects a meaningful but not critical risk profile: the attack is network-accessible with low complexity and no required user interaction, but it does require authenticated low-privilege access (PR:L), which is the primary limiting factor. The impact model shows no direct vulnerable-system compromise (VC:N/VI:N/VA:N) but high subsequent-system confidentiality impact (SC:H), accurately capturing the SSRF scenario where the attacker reads responses from internal services rather than directly compromising Flyto Core itself. There is no EPSS score included in the input data, and the vulnerability is not listed in the CISA KEV catalog, indicating no confirmed mass or opportunistic exploitation at this time. No public proof-of-concept code has been identified, which modestly lowers near-term automated exploitation risk. That said, even a mid-sized municipal IT team in olsztyn operating internal tooling or microservices accessible on IPv6 loopback should treat this as a meaningful remediation priority, since any authenticated user of Flyto Core - including low-privilege service accounts - could pivot to internal APIs, metadata endpoints, or administrative services otherwise unreachable from outside the host. The SSRF vector is conceptually simple and the bypass technique (using :: instead of 127.0.0.1) is a well-understood class of guard evasion, meaning the bar for exploitation post-disclosure is low even without a published PoC.

Exploit ScenarioDerived

An attacker with low-privilege authenticated access to a Flyto Core deployment submits an HTTP request to one of the http.get, http.request, or http.batch modules with a target URL of http://[::]/admin or a URL that redirects via a 302 to http://[::]:<port>/. Because is_private_ip() does not classify :: as a private or loopback address, the guard passes the request, and the server-side HTTP client connects to the internal IPv6 loopback interface, returning the response of any service bound there - such as a local admin panel, metadata API, or internal microservice - directly to the attacker. No public proof-of-concept code has been identified, but the technique requires only knowledge of the :: loopback routing behavior, which is publicly documented.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Aug 13, 2026

Server-side request forgery guard bypass in Flyto Core (flyto-core) versions up to and including 2.27.0 allows authenticated low-privilege attackers to reach internal network services by supplying the IPv6 unspecified address ::, which the OS kernel routes to loopback identically to 0.0.0.0. The is_private_ip() guard function fails to classify :: or its expanded spellings as private, and the bypass is also reachable via attacker-controlled 302 redirects, meaning the attack surface spans the http.get, http.request, and http.batch modules. A vendor-released patch is available in v2.28.0; no public exploit code or CISA KEV listing has been identified at time of analysis.

RemediationAI

Upgrade flyto-core to version 2.28.0 immediately using python -m pip install --upgrade flyto-core==2.28.0, as confirmed by the vendor release at https://github.com/flytohub/flyto-core/releases/tag/v2.28.0 and the advisory at https://github.com/flytohub/flyto-core/security/advisories/GHSA-gc4h-hj7x-gp5p. If immediate upgrade is not possible, restrict who can supply URLs to the http.get, http.request, and http.batch modules - specifically, revoke or limit low-privilege accounts that can submit external URLs or trigger HTTP requests through Flyto Core, as this eliminates the PR:L attack surface. Additionally, consider deploying network-layer egress controls on hosts running Flyto Core to block loopback-destined outbound connections from the application process, though this may disrupt legitimate local inter-process communication and requires testing. Disabling IPv6 on the host (sysctl -w net.ipv6.conf.all.disable_ipv6=1) would prevent routing of :: to loopback but carries significant operational side effects if other services depend on IPv6 and is not a substitute for patching.

Affected VersionsENISA

flyto-core 0 <2.28.0

Affected Packages

euvd flyto_core fix: 2.28.0

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Flyto Core (CPE: cpe:2.3:a:flytohub:flyto-core:*:*:*:*:*:*:*:*) is a Python package installable via pip that provides HTTP utility modules (http.get, http.request, http.batch) with an SSRF guard implemented in the is_private_ip() function. The root cause is CWE-918 (Server-Side Request Forgery): the guard correctly blocks IPv4 private ranges and loopback (0.0.0.0, 127.0.0.1) and common private hostnames, but omits the IPv6 unspecified address :: and its canonically expanded equivalents (e.g., 0000:0000:0000:0000:0000:0000:0000:0000). Because the Linux and POSIX kernel network stacks route :: to the IPv6 loopback interface (::1) - analogous to how 0.0.0.0 routes to 127.0.0.1 on IPv4 - an attacker-supplied URL containing :: successfully contacts services bound to the IPv6 loopback. The bypass is also reachable via HTTP 302 redirect chains that resolve to :: after the initial URL guard check, a classic SSRF redirect-follow anti-pattern. The fix in v2.28.0 extends the shared address classifier to reject both IPv4 and IPv6 unspecified addresses and all expanded IPv6 representations of those addresses before any HTTP module processes the URL.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (VulnCheck) PRIMARY 6.3 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N
vuln.today AI 7.7 HIGH

PR:L for required authenticated access; S:C and C:H capture SSRF reaching internal IPv6 loopback services beyond the application boundary; no integrity or availability impact confirmed.

3.1 AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
Low
User Interaction
None
Vulnerable system: Confidentiality
None
Vulnerable system: Integrity
None
Vulnerable system: Availability
None
Subsequent system: Confidentiality
High
Subsequent system: Integrity
None
Subsequent system: Availability
None

Lifecycle Timeline

1
Patch available
Aug 13, 2026 - 20:19 EUVD

DescriptionCVE.org

Flyto2 Core before 2.28.0 contains a server-side request forgery guard bypass vulnerability that allows attackers to reach internal services by supplying URLs using the unblocked IPv6 address :: which the kernel routes to loopback identically to 0.0.0.0. Attackers can submit requests or trigger 302 redirects to to bypass the private IP range and blocked hostname checks in is_private_ip(), reaching services bound to IPv6 loopback across the http.get, http.request, and http.batch` modules.

Threat Intelligence Overview

EPSS Score
0.3%
Top 76% exploitable
Prevalence
Low
niche Python workflow package, limited public deployment footprint
Data Quality
6 sources
Confidence: High

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.3%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
Poc
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

32
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +32
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Server-Side Request Forgery exploits applications that fetch remote resources based on user-supplied URLs.

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