Vulnerability · Published Sep 7, 2026 · Assigned by EEF
CVE-2026-82757ash_authentication_oauth2_server CIMD fetcher classifies IPv4-in-IPv6 and site-local addresses as public, allowing SSRF
Medium 6.3
In plain English
A medium-severity server-side request forgery in ash_authentication_oauth2_server from ash-project. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 52% of all known vulnerabilities).
Official 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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| ash-project | ash_authentication_oauth2_server | 0.3.0 – before 0.3.1 |
| ash-project | ash_authentication_oauth2_server | e713a9ba816761140c226e2ca55b75c0b93f5984 – before 268b591261a3473ab9b87272963e4dd2fd99d972 |
Weakness: CWE-918 · Vector: 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
References
- https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-wprp-8gvj-p6cv vendor-advisory, related
- https://cna.erlef.org/cves/CVE-2026-82757.html related
- https://osv.dev/vulnerability/EEF-CVE-2026-82757 related
- https://github.com/ash-project/ash_authentication_oauth2_server/commit/268b591261a3473ab9b87272963e4dd2fd99d972 patch