CVE-2022-36009 – Incorrect parsing of access level in gomatrixserverlib and dendrite

https://notcve.org/view.php?id=CVE-2022-36009

gomatrixserverlib is a Go library for matrix protocol federation. Dendrite is a Matrix homeserver written in Go, an alternative to Synapse. The power level parsing within gomatrixserverlib was failing to parse the `"events_default"` key of the `m.room.power_levels` event, defaulting the event default power level to zero in all cases. Power levels are the matrix terminology for user access level. In rooms where the `"events_default"` power level had been changed, this could result in events either being incorrectly authorised or rejected by Dendrite servers. gomatrixserverlib contains a fix as of commit `723fd49` and Dendrite 0.9.3 has been updated accordingly. • https://github.com/matrix-org/gomatrixserverlib/commit/723fd495dde835d078b9f2074b6b62c06dea4575 https://github.com/matrix-org/gomatrixserverlib/security/advisories/GHSA-grvv-h2f9-7v9c https://matrix.org/docs/guides/moderation/#power-levels • CWE-863: Incorrect Authorization •