CVE-2026-82757
CVE-2026-82757 — ash_authentication_oauth2_server CIMD fetcher classifies IPv4-in-IPv6 and site-local addresses as public, allowing SSRF
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.
Published Updated Sources: cvelistV5, EEF
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.
Exploitation
Unreported
no source claims exploitation
EPSS
0%
chance of exploitation in 30 days
CVSS base
6.3
MEDIUM
CISA SSVC assessment
Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.
Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script all four kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component
Affected scope
The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.
Vendors (1)
Products (1)
Every base score collected
Sources score independently and disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Source |
|---|---|---|---|---|---|
| 6.3 | CVSS 4.0 | MEDIUM | — | — | cvelistV5 |
Weakness & attack patterns
- CWE-918
Detection
Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.
- Search application, proxy, and WAF logs for requests touching /1, /96, /10.
References
4 on the record
- github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-wprp-8gvj-p6cv
vendor-advisory, related
- cna.erlef.org/cves/CVE-2026-82757.html
related
- osv.dev/vulnerability/EEF-CVE-2026-82757
related
- github.com/ash-project/ash_authentication_oauth2_server/commit/268b591261a3473ab9b87272963e4dd2fd99d972
patch
Elsewhere on this site
- ash projectevery CVE for this vendor
- CWE-918other pages naming this weakness
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.