Unverified Sign in with Apple callback parameter can override verified ID token claims (pow-auth assent)
At a glance
- Source
- NVD
- State
- PUBLISHED
- Published
- Updated
- Assigner
- EEF
- NVD status
- Received
Description
Acceptance of Extraneous Untrusted Data With Trusted Data vulnerability in the Sign in with Apple strategy in pow-auth Assent allows an unauthenticated remote attacker to impersonate another user via the user parameter of the authorization callback. Apple posts the user's name to the callback endpoint in a user form parameter that the browser submits and the client controls. Assent.Strategy.Apple.callback/2 in lib/assent/strategies/apple.ex decodes that parameter, and fetch_user/2 merges it over the claims of the verified ID token, so the unverified map wins. An attacker who completes a Sign in with Apple login with their own Apple ID and edits the user parameter can replace sub, email, and any other claim. Applications that look up, link, or authorize accounts by the returned subject or email then act on the attacker's values. This issue affects assent: from 0.1.25 before 0.3.2.
Weaknesses (CWE)
- CWE-290 — Authentication Bypass by Spoofing
- CWE-349 — Acceptance of Extraneous Untrusted Data With Trusted Data
References
- https://github.com/pow-auth/assent/security/advisories/GHSA-9fr5-g44g-9526
- https://cna.erlef.org/cves/CVE-2026-117656.html
- https://osv.dev/vulnerability/EEF-CVE-2026-117656
- https://github.com/pow-auth/assent/commit/a2d331e8c51376d6c0b04a81aad31e0b4d4d64a3
- https://github.com/pow-auth/assent/commit/18898bde0296152165ae470078490e5798329b1b
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 4.0 | CRITICAL 9.3 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N | EEF |
| CVSS 4.0 | CRITICAL 9.3 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/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 | NVD · 6b3ad84c-e1a6-4bf7-a703-f496b71e49db (Secondary) |
European references
- ENISA EUVD · EUVD-2026-114568
- GCVE · GCVE-0-2026-117656
Affected products
| Product | Versions |
|---|---|
| pow-auth · assent | affected 0.1.25 < 0.3.2 |
| pow-auth · assent | affected a2d331e8c51376d6c0b04a81aad31e0b4d4d64a3 < 18898bde0296152165ae470078490e5798329b1b |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |