CVE-2026-27838: wger: IDOR via user-unscoped cache keys on routine API actions exposes workout data

Summary

Five routine detail action endpoints check a cache before calling self.getobject(). Cache keys are scoped only by pk — no user ID is included. When a victim has previously accessed their routine via the API, an attacker can retrieve the cached response for the same PK without any ownership check.

Details

wger/manager/api/views.py — five actions follow this pattern (lines 134–201):

python @action(detail=True) def datesequencedisplaymode(self, request, pk=None): cachekey = makeroutineapidatesequencedisplaycachekey(pk) cached = cache.get(cachekey) if cached: return Response(cached) # returned WITHOUT calling self.getobject() # only reaches ownership check on cache miss routine = self.getobject() ...

Cache key construction in wger/utils/cache.py:89–106:

python def makeroutineapidatesequencedisplaycachekey(routineid): return f"routine-api-date-sequence-display-{routineid}" # No user ID in key

Cache TTL: 1 month (4 604800 seconds, settingsglobal.py:461).

Affected endpoints: GET /api/v2/routine/{pk}/date-sequence-display/ GET /api/v2/routine/{pk}/date-sequence-gym/ GET /api/v2/routine/{pk}/structure/ GET /api/v2/routine/{pk}/logs/ GET /api/v2/routine/{pk}/stats/

PoC

1. Victim (user A) visits GET /api/v2/routine/5/structure/ → response cached under key "routine-api-structure-5" 2. Attacker (user B) visits GET /api/v2/routine/5/structure/ → cache hit → returns user A's routine structure without any ownership check

Requires the victim to have previously accessed the endpoint (cache must be populated). Once populated, the cache entry is valid for 1 month.

Impact

An attacker with a registered account can retrieve another user's routine details — workout day sequences, exercise structure, training logs, and statistics — from cache without ownership verification.

Fix: Include the user ID in the cache key: python def makeroutineapidatesequencedisplaycachekey(routineid, userid): return f"routine-api-date-sequence-display-{userid}-{routineid}"

Or move self.getobject() before the cache lookup so ownership is always verified first.