{"id":"CVE-2022-39257","aliases":["EUVD-2022-41769","GHSA-qxr3-5jmq-xcf4"],"status":"published","title":"Matrix iOS SDK vulnerable to impersonation via forwarded Megolm sessions","description":"Matrix iOS SDK allows developers to build iOS apps compatible with Matrix. Prior to version 0.23.19, an attacker cooperating with a malicious homeserver can construct messages appearing to have come from another person. Such messages will be marked with a grey shield on some platforms, but this may be missing in others. This attack is possible due to the matrix-ios-sdk implementing a too permissive key forwarding strategy. The default policy for accepting key forwards has been made more strict in the matrix-ios-sdk version 0.23.19. matrix-ios-sdk will now only accept forwarded keys in response to previously issued requests and only from own, verified devices. The SDK now sets a `trusted` flag on the decrypted message upon decryption, based on whether the key used to decrypt the message was received from a trusted source. Clients need to ensure that messages decrypted with a key with `trusted = false` are decorated appropriately (for example, by showing a warning for such messages). This attack requires coordination between a malicious home server and an attacker, so those who trust their home servers do not need a workaround.","severity":{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00996,"percentile":0.63115,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-287","CWE-322"],"published":"2022-09-28T20:55:10Z","modified":"2026-10-28T10:27:31Z","products":[{"vendor":"matrix","product":"software_development_kit"},{"vendor":"matrix-org","product":"matrix-ios-sdk"}],"references":[{"url":"https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients","tags":["x_refsource_MISC","x_transferred","Vendor Advisory","article"]},{"url":"https://github.com/matrix-org/matrix-ios-sdk/commit/5ca86c328a5faaab429c240551cb9ca8f0f6262c","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix"]},{"url":"https://github.com/matrix-org/matrix-ios-sdk/releases/tag/v0.23.19","tags":["x_refsource_MISC","x_transferred","Release Notes","Third Party Advisory","web"]},{"url":"https://github.com/matrix-org/matrix-ios-sdk/security/advisories/GHSA-qxr3-5jmq-xcf4","tags":["x_refsource_CONFIRM","x_transferred","Third Party Advisory","advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2022/39xxx/CVE-2022-39257.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2022-39257","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2022-39257","title":"Matrix iOS SDK vulnerable to impersonation via forwarded Megolm sessions","description":"Matrix iOS SDK allows developers to build iOS apps compatible with Matrix. Prior to version 0.23.19, an attacker cooperating with a malicious homeserver can construct messages appearing to have come from another person. Such messages will be marked with a grey shield on some platforms, but this may be missing in others. This attack is possible due to the matrix-ios-sdk implementing a too permissive key forwarding strategy. The default policy for accepting key forwards has been made more strict in the matrix-ios-sdk version 0.23.19. matrix-ios-sdk will now only accept forwarded keys in response to previously issued requests and only from own, verified devices. The SDK now sets a `trusted` flag on the decrypted message upon decryption, based on whether the key used to decrypt the message was received from a trusted source. Clients need to ensure that messages decrypted with a key with `trusted = false` are decorated appropriately (for example, by showing a warning for such messages). This attack requires coordination between a malicious home server and an attacker, so those who trust their home servers do not need a workaround.","status":"published","published":"2022-09-28T20:55:10Z","modified":"2025-04-23T16:54:28.718Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"cna"}],"cwes":["CWE-322","CWE-287"],"updated_at":"2026-11-02T14:34:39.559326Z"}],"euvd":[{"id":"EUVD-2022-41769","description":"Matrix iOS SDK allows developers to build iOS apps compatible with Matrix. Prior to version 0.23.19, an attacker cooperating with a malicious homeserver can construct messages appearing to have come from another person. Such messages will be marked with a grey shield on some platforms, but this may be missing in others. This attack is possible due to the matrix-ios-sdk implementing a too permissive key forwarding strategy. The default policy for accepting key forwards has been made more strict in the matrix-ios-sdk version 0.23.19. matrix-ios-sdk will now only accept forwarded keys in response to previously issued requests and only from own, verified devices. The SDK now sets a `trusted` flag on the decrypted message upon decryption, based on whether the key used to decrypt the message was received from a trusted source. Clients need to ensure that messages decrypted with a key with `trusted = false` are decorated appropriately (for example, by showing a warning for such messages). This attack requires coordination between a malicious home server and an attacker, so those who trust their home servers do not need a workaround.","status":"published","published":"2022-09-28T20:55:10Z","modified":"2025-04-23T16:54:28Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"}],"updated_at":"2026-11-02T20:52:11.440801Z"}],"nvd":[{"id":"CVE-2022-39257","description":"Matrix iOS SDK allows developers to build iOS apps compatible with Matrix. Prior to version 0.23.19, an attacker cooperating with a malicious homeserver can construct messages appearing to have come from another person. Such messages will be marked with a grey shield on some platforms, but this may be missing in others. This attack is possible due to the matrix-ios-sdk implementing a too permissive key forwarding strategy. The default policy for accepting key forwards has been made more strict in the matrix-ios-sdk version 0.23.19. matrix-ios-sdk will now only accept forwarded keys in response to previously issued requests and only from own, verified devices. The SDK now sets a `trusted` flag on the decrypted message upon decryption, based on whether the key used to decrypt the message was received from a trusted source. Clients need to ensure that messages decrypted with a key with `trusted = false` are decorated appropriately (for example, by showing a warning for such messages). This attack requires coordination between a malicious home server and an attacker, so those who trust their home servers do not need a workaround.","status":"published","published":"2022-09-28T21:15:14.397Z","modified":"2026-06-17T04:58:00.83Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"primary"}],"cwes":["CWE-287","CWE-322"],"updated_at":"2026-11-02T14:07:29.026521Z"}],"osv":[{"id":"CVE-2022-39257","title":"Matrix iOS SDK vulnerable to impersonation via forwarded Megolm sessions","description":"Matrix iOS SDK allows developers to build iOS apps compatible with Matrix. Prior to version 0.23.19, an attacker cooperating with a malicious homeserver can construct messages appearing to have come from another person. Such messages will be marked with a grey shield on some platforms, but this may be missing in others. This attack is possible due to the matrix-ios-sdk implementing a too permissive key forwarding strategy. The default policy for accepting key forwards has been made more strict in the matrix-ios-sdk version 0.23.19. matrix-ios-sdk will now only accept forwarded keys in response to previously issued requests and only from own, verified devices. The SDK now sets a `trusted` flag on the decrypted message upon decryption, based on whether the key used to decrypt the message was received from a trusted source. Clients need to ensure that messages decrypted with a key with `trusted = false` are decorated appropriately (for example, by showing a warning for such messages). This attack requires coordination between a malicious home server and an attacker, so those who trust their home servers do not need a workaround.","status":"published","published":"2022-09-28T20:55:10Z","modified":"2026-10-28T10:27:31.742879496Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"}],"cwes":["CWE-287","CWE-322"],"updated_at":"2026-11-02T15:44:26.53798Z"}]}}