{"id":"CVE-2026-76236","aliases":["GHSA-x26h-xmv8-gxf7"],"url":"https://o3.security/vulnerability/CVE-2026-76236","summary":"stigmem before 0.9.0a12 Cross-Tenant BOLA via Tombstones","details":"### Summary\nOn a multi-tenant stigmem node, RTBF (right-to-be-forgotten) tombstones were mis-scoped two ways. (1) `issue_tombstone` defaulted the tenant to `\"default\"` instead of the caller's tenant, so tombstones could be written to the wrong tenant. (2) The read-suppression path — `_get_tombstone_filter` (`routes/facts/common.py`) and the `_tombstone_scope_cache` (`lifecycle/tombstones.py`) — had no `tenant_id` predicate, so tombstone suppression was applied tenant-blind across fact queries and provenance. Reached via `/v1/tombstones` and the fact query/provenance read paths.\n\n### Impact\nCross-tenant integrity of the RTBF mechanism: a tenant's deletion request could be recorded against the wrong tenant, and tombstone suppression could hide — or fail to hide — facts across tenant boundaries, undermining both data-view correctness and RTBF guarantees.\n\n### Affected configurations\nThis is a cross-**tenant** break. It is exploitable **only** on deployments running the opt-in `stigmem-plugin-multi-tenant` (multiple tenants on one node). A default single-tenant node has only `tenant=\"default\"` — there is no second tenant to cross — so it is **not exploitable** on default deployments. The rating is HIGH for the multi-tenant deployments the plugin exists to isolate.\n\n### Patches\nFixed in `0.9.0a12` (PR #728): `identity.tenant_id` is passed from `issue_tombstone` into `create_tombstone` (no more `\"default\"` fallback); `AND tenant_id = ?` was added to `_get_tombstone_filter` and `get_tombstone_status`; the suppression cache is re-keyed to include tenant; and all four read call sites thread the caller's tenant. A tenant-B tombstone now suppresses only tenant-B facts and is invisible to tenant-A reads.\n\n### Workarounds\nNone other than upgrading to `0.9.0a12`. Single-tenant deployments are unaffected.","published":"2026-08-19T14:02:15.209Z","modified":"2026-10-28T02:30:38.696952714Z","cvss":null,"epss":{"score":0.00265,"percentile":0.18616,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"stigmem-node","fixedVersion":"0.9.0a12"}],"fix":{"url":"https://github.com/eidetic-labs/stigmem/pull/728","label":"eidetic-labs/stigmem#728"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/76xxx/CVE-2026-76236.json"},{"type":"ADVISORY","url":"https://github.com/eidetic-labs/stigmem/security/advisories/GHSA-x26h-xmv8-gxf7"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-76236"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/stigmem-before-0a12-cross-tenant-bola-via-tombstones"},{"type":"WEB","url":"https://github.com/eidetic-labs/stigmem/pull/728"},{"type":"PACKAGE","url":"https://github.com/eidetic-labs/stigmem"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:30:38.696952714Z"}}