CVE-2026-27838

Five routine detail action endpoints check a cache before calling self.get_object(). 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):

@action(detail=True)
def date_sequence_display_mode(self, request, pk=None):
    cache_key = make_routine_api_date_sequence_display_cache_key(pk)
    cached = cache.get(cache_key)
    if cached:
        return Response(cached)   # returned WITHOUT calling self.get_object()
    # only reaches ownership check on cache miss
    routine = self.get_object()
    ...

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

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

Cache TTL: 1 month (4 * 604800 seconds, settings_global.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.

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:

def make_routine_api_date_sequence_display_cache_key(routine_id, user_id):
    return f"routine-api-date-sequence-display-{user_id}-{routine_id}"

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

CVE-2026-27838 has a CVSS score of 3.1 (Low). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Kodem intelligence

1. What is CVE-2026-27838? CVE-2026-27838 is a low-severity security vulnerability in wger (pip), affecting versions <= 2.1. No fixed version is listed yet.
2. How severe is CVE-2026-27838? CVE-2026-27838 has a CVSS score of 3.1 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of wger are affected by CVE-2026-27838? wger (pip) versions <= 2.1 is affected.
4. Is there a fix for CVE-2026-27838? No fixed version is listed for CVE-2026-27838 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2026-27838 exploitable, and should I be worried? Whether CVE-2026-27838 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-27838 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.