CVE-2026-82757
ash_authentication_oauth2_server CIMD fetcher classifies IPv4-in-IPv6 and site-local addresses as public, allowing SSRF
- State
- Published
- Severity
- 6.3 Medium
- Published
- Sep 7, 2026
- Updated
- Sep 8, 2026
- Reserved
- Aug 31, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 6.3 Medium | 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 | EEF |
Weaknesses
- CWE-918 Server-Side Request Forgery (SSRF)
Affected Products
| Product | Versions |
|---|---|
ash_authentication_oauth2_serverash-project |
|
ash_authentication_oauth2_serverash-project |
|
References
- https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-wprp-8gvj-p6cvvendor-advisoryrelated
- https://cna.erlef.org/cves/CVE-2026-82757.htmlrelated
- https://osv.dev/vulnerability/EEF-CVE-2026-82757related
- https://github.com/ash-project/ash_authentication_oauth2_server/commit/268b591261a3473ab9b87272963e4dd2fd99d972patch
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