EEF-CVE-2026-82757 CVE-2026-82757 GHSA-wprp-8gvj-p6cv
ash_authentication_oauth2_server CIMD fetcher classifies IPv4-in-IPv6 and site-local addresses as public, allowing SSRF
- Severity
- 0.0 / 10
- Unknown · CVSS 4.0
- Exploit chance (EPSS)
- 0.66%
- Chance of exploitation in the next 30 days. Higher than 51.78% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-918 Server-Side Request Forgery (SSRF)
- Fix
0.3.1- Upgrade ash_authentication_oauth2_server to this version or later
Description
Summary
Server-Side Request Forgery (SSRF) vulnerability in ash-project ash_authentication_oauth2_server allows an attacker who controls a client metadata URL and its DNS to make the server connect to internal or loopback addresses.
public_ip?/1 in AshAuthentication.Oauth2Server.CIMD.ReqFetcher enforces the outbound policy for CIMD metadata fetches. It classified several address forms as publicly routable that are not: IPv4-compatible ::/96 (for example ::127.0.0.1), SIIT IPv4-translated ::ffff:0:0:0/96, and deprecated site-local fec0::/10. A returned AAAA record in one of these ranges passed the policy, so a fetch pinned to that address reached space the policy was meant to block.
This issue affects ash_authentication_oauth2_server: from 0.3.0 before 0.3.1.
Configurations
Reachable only when Client ID Metadata Documents are enabled (cimd_enabled?: true), so the authorize endpoint fetches attacker-suppliable metadata URLs, and an internal or loopback target resolves to one of the affected IPv6 address forms.
Affected versions
Hex
| Package | Vulnerable | Fixed in |
|---|---|---|
| ash_authentication_oauth2_server | >= 0.3.0, < 0.3.1 |
0.3.1 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
ash_authentication_oauth2_server Hex → 0.3.1
- mix
{:ash_authentication_oauth2_server, "~> 0.3.1"} # then: mix deps.update ash_authentication_oauth2_server
Severity breakdown
CVSS 4.0 0.0
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- Present
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- None
- Confidentiality (subsequent systems)
- Low
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
Weakness
CWE-918: 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.
References
Advisories
Fixes and patches
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| EEF-CVE-2026-82758 ash_authentication_oauth2_server treats an empty resolved secret as valid, opening the gated Dynamic Client Registration endpoint | Not rated yet | Also affects ash_authentication_oauth2_server |
| EEF-CVE-2026-82756 ash_authentication_oauth2_server interpolates a tenant-derived value into the WWW-Authenticate challenge without escaping, allowing header parameter injection | Not rated yet | Also affects ash_authentication_oauth2_server |
| EEF-CVE-2026-82755 ash_authentication_oauth2_server serves tenant-specific OAuth metadata as publicly cacheable without Vary, enabling cross-tenant confusion | Not rated yet | Also affects ash_authentication_oauth2_server |
| EEF-CVE-2026-82754 ash_authentication_oauth2_server aliases every protocol endpoint under /.well-known, bypassing path-scoped controls | Not rated yet | Also affects ash_authentication_oauth2_server |
| EEF-CVE-2026-82753 Unauthenticated authorize requests create unbounded, never-expiring CIMD client rows and cache entries in ash_authentication_oauth2_server | Not rated yet | Also affects ash_authentication_oauth2_server |
| EEF-CVE-2026-115700 SSRF allowlist bypass via percent-encoded bracketed IPv6 or trailing-dot IP literal in hackney | Not rated yet | Same weakness, CWE-918 |
| GHSA-2wqp-q3c6-ccj5 MLflow: SSRF on unauthenticated MLflow servers via third-party scorer kwargs in the scorer invoke, register, and GenAI evaluate endpoints | Medium | Same weakness, CWE-918 |
| GHSA-2phh-27fw-q4gc PhpSpreadsheet: SSRF whitelist bypass via unre-validated HTTP redirect in Drawing::setPath external image loading | Medium | Same weakness, CWE-918 |
Credits: Jonatan Männchen / EEF, Peter Ullrich, Zach Daniel / Ash Project
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