{"cve":"CVE-2021-32659","nvd":{"published":"2021-06-16T19:15:38.830","modified":"2026-06-17T03:53:22.010","status":"Modified","description":"Matrix-appservice-bridge is the bridging service for the Matrix communication program's application services. In versions 2.6.0 and earlier, if a bridge has room upgrade handling turned on in the configuration (the `roomUpgradeOpts` key when instantiating a new `Bridge` instance.), any `m.room.tombstone` event it encounters will be used to unbridge the current room and bridge into the target room. However, the target room `m.room.create` event is not checked to verify if the `predecessor` field contains the previous room. This means that any malicious admin of a bridged room can repoint the traffic to a different room without the new room being aware. Versions 2.6.1 and greater are patched. As a workaround, disabling the automatic room upgrade handling can be done by removing the `roomUpgradeOpts` key from the `Bridge` class options.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N","score":4.9},"cwes":["CWE-306"],"references":["https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9f","https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1","https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhx","https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9f","https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1"],"products":["matrix:matrix-appservice-bridge"],"source":"nvd","synced_at":"2026-10-19T21:20:07.141963181+00:00"},"epss":{"cve":"CVE-2021-32659","score":0.00936,"percentile":0.60821,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-35g4-qx3c-vjhx","url":"https://osv.dev/vulnerability/GHSA-35g4-qx3c-vjhx","summary":"Automatic room upgrade handling can be used maliciously to bridge a room non-consentually ","modified":"2026-07-08T06:29:05.568084068Z","packages":[{"ecosystem":"npm","name":"matrix-appservice-bridge","purl":"pkg:npm/matrix-appservice-bridge","ranges":["<2.6.1"],"fixed":["2.6.1"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}