CVE-2026-28789

### Summary An unauthenticated denial-of-service vulnerability exists in OliveTin’s OAuth2 login flow. Concurrent requests to /oauth/login can trigger unsynchronized access to a shared registeredStates map, causing a Go runtime panic (fatal error: concurrent map writes) and process termination. This allows remote attackers to crash the service when OAuth2 is enabled. ### Details The OAuth2 handler stores per-login state in a shared map without synchronization: - service/internal/auth/otoauth2/restapi_auth_oauth2.go:24 registeredStates map[string]*oauth2State - Unlocked write in login handler: .../restapi_auth_oauth2.go:141 - Unlocked read in callback check: .../restapi_auth_oauth2.go:174 - Unlocked writes in callback flow: .../restapi_auth_oauth2.go:284-285 - Unlocked read in auth chain check: .../restapi_auth_oauth2.go:376 These paths are network reachable via publicly registered routes: ```bash - service/internal/httpservers/frontend.go:71 → /oauth/login - service/internal/httpservers/frontend.go:72 → /oauth/callback ``` Because Go HTTP handlers run concurrently, high parallel traffic to /oauth/login causes concurrent map access and runtime panic. Tested on: - Container image: ghcr.io/olivetin/olivetin:3000.10.0 - Source also contains same pattern at commit/tag eb42029b5d0c0633551621288180dd4566b913f7 (3000.10.1) ### PoC 1. Start OliveTin with OAuth2 provider configured (example github), exposing port 1337. 2. Confirm baseline: ```bash curl -i http://127.0.0.1:1337/readyz curl -i "http://127.0.0.1:1337/oauth/login?provider=github" ``` Expected: 200 for /readyz, 302 for /oauth/login. 3. Run concurrency PoC: ```bash python3 /OliveTin/tools/poc_oauth2_state_map_race_dos.py \ --base-url http://127.0.0.1:1337 \ --provider github \ --workers 80 \ --requests 120000 \ --health-failures 3 ``` 4. Verify crash: docker inspect olivetin-dos --format 'status={{.State.Status}} exit={{.State.ExitCode}}' docker logs olivetin-dos 2>&1 | grep -E "fatal error: concurrent map|concurrent map writes|restapi_auth_oauth2.go" Observed result: - Process exited with code 2 - Logs include: - fatal error: concurrent map writes - .../internal/auth/otoauth2/restapi_auth_oauth2.go:141 in HandleOAuthLogin ### Impact - Vulnerability type: Race condition (CWE-362) leading to DoS. - Attacker requirements: network access only; no authentication required for exploit path. - Impacted deployments: OliveTin instances with OAuth2 enabled and reachable over network. - Security impact: remote unauthenticated attacker can repeatedly crash OliveTin, causing availability loss until restart/recovery. [poc_oauth2_state_map_race_dos.py](https://github.com/user-attachments/files/25577901/poc_oauth2_state_map_race_dos.py)

OliveTin has unauthenticated DoS via concurrent map writes in OAuth2 state handling in github.com/OliveTin/OliveTin. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. (If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.) The additional affected modules and versions are: github.com/OliveTin/OliveTin before v0.0.0-20260301235225-f044d90d5525c.