{"id":"CVE-2021-34813","aliases":["DEBIAN-CVE-2021-34813","EUVD-2021-21460","GHSA-269w-9hm6-g22q","UBUNTU-CVE-2021-34813","USN-5194-1"],"status":"published","title":"Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is...","description":"Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is attempting to retrieve an Olm encrypted room key backup from the homeserver) because olm_pk_decrypt has a stack-based buffer overflow. Remote code execution might be possible for some nonstandard build configurations.","severity":{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-10","score":0.04262,"percentile":0.91146,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-787"],"published":"2021-06-16T17:11:53Z","modified":"2026-10-23T18:03:38Z","fixes":[{"ecosystem":"Debian:12","package":"olm","fixed_in":["3.2.3~dfsg-3"],"sources":["osv"]},{"ecosystem":"Debian:13","package":"olm","fixed_in":["3.2.3~dfsg-3"],"sources":["osv"]},{"ecosystem":"Debian:14","package":"olm","fixed_in":["3.2.3~dfsg-3"],"sources":["osv"]},{"ecosystem":"Ubuntu:Pro:20.04:LTS","package":"olm","fixed_in":["3.1.3+dfsg-2ubuntu0.1~esm1"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Debian:12","package":"olm","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.2.3~dfsg-3"}]}]},{"source":"osv","ecosystem":"Debian:13","package":"olm","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.2.3~dfsg-3"}]}]},{"source":"osv","ecosystem":"Debian:14","package":"olm","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.2.3~dfsg-3"}]}]},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"olm","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.3+dfsg-2ubuntu0.1~esm1"}]}],"versions":["3.1.3+dfsg-2","3.1.3+dfsg-2build1","3.1.3+dfsg-2build2"]},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"olm","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.3+dfsg-2ubuntu0.1~esm1"}]}],"versions":["3.1.3+dfsg-2","3.1.3+dfsg-2build1","3.1.3+dfsg-2build2"]}],"products":[{"vendor":"matrix","product":"olm"}],"references":[{"url":"https://matrix.org/blog/2021/06/14/adventures-in-fuzzing-libolm","tags":["x_refsource_MISC","x_transferred","Exploit","Patch","Vendor Advisory","fix","report"]},{"url":"https://gitlab.matrix.org/matrix-org/olm/-/releases/3.2.3","tags":["x_refsource_MISC","x_transferred","Release Notes","Vendor Advisory","advisory","report"]},{"url":"https://gitlab.matrix.org/matrix-org/olm/-/commit/ccc0d122ee1b4d5e5ca4ec1432086be17d5f901b","tags":["x_refsource_MISC","x_transferred","Patch","Vendor Advisory","fix","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-34813"},{"url":"https://github.com/advisories/GHSA-269w-9hm6-g22q"},{"url":"https://security-tracker.debian.org/tracker/CVE-2021-34813","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2021-34813","tags":["report"]},{"url":"https://ubuntu.com/security/notices/USN-5194-1","tags":["advisory"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-34813","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2021-34813","description":"Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is attempting to retrieve an Olm encrypted room key backup from the homeserver) because olm_pk_decrypt has a stack-based buffer overflow. Remote code execution might be possible for some nonstandard build configurations.","status":"published","published":"2021-06-16T17:11:53Z","modified":"2024-08-04T00:26:54.02Z","updated_at":"2026-11-02T14:33:11.244759Z"}],"euvd":[{"id":"EUVD-2021-21460","description":"Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is attempting to retrieve an Olm encrypted room key backup from the homeserver) because olm_pk_decrypt has a stack-based buffer overflow. Remote code execution might be possible for some nonstandard build configurations.","status":"published","published":"2021-06-16T17:11:53Z","modified":"2024-08-04T00:26:54Z","updated_at":"2026-11-03T03:24:31.977228Z"}],"ghsa":[{"id":"GHSA-269w-9hm6-g22q","title":"Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is...","description":"Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is attempting to retrieve an Olm encrypted room key backup from the homeserver) because olm_pk_decrypt has a stack-based buffer overflow. Remote code execution might be possible for some nonstandard build configurations.","status":"published","published":"2022-05-24T19:05:26Z","modified":"2023-01-29T05:07:01Z","cwes":["CWE-787"],"updated_at":"2026-11-02T14:46:08.233339Z"}],"nvd":[{"id":"CVE-2021-34813","description":"Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is attempting to retrieve an Olm encrypted room key backup from the homeserver) because olm_pk_decrypt has a stack-based buffer overflow. Remote code execution might be possible for some nonstandard build configurations.","status":"published","published":"2021-06-16T18:15:09.73Z","modified":"2026-06-17T03:56:36.99Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"primary"},{"version":"2.0","score":7.5,"vector":"AV:N/AC:L/Au:N/C:P/I:P/A:P","level":"high","assessor":"primary"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T14:06:54.892562Z"}],"osv":[{"id":"CVE-2021-34813","description":"Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is attempting to retrieve an Olm encrypted room key backup from the homeserver) because olm_pk_decrypt has a stack-based buffer overflow. Remote code execution might be possible for some nonstandard build configurations.","status":"published","published":"2021-06-16T18:15:09.73Z","modified":"2026-10-20T14:04:47.489600529Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:44:20.13324Z"},{"id":"DEBIAN-CVE-2021-34813","description":"Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is attempting to retrieve an Olm encrypted room key backup from the homeserver) because olm_pk_decrypt has a stack-based buffer overflow. Remote code execution might be possible for some nonstandard build configurations.","status":"published","published":"2021-06-16T18:15:09.73Z","modified":"2026-10-23T18:03:38.285172635Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:45:35.233346Z"},{"id":"UBUNTU-CVE-2021-34813","description":"Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is attempting to retrieve an Olm encrypted room key backup from the homeserver) because olm_pk_decrypt has a stack-based buffer overflow. Remote code execution might be possible for some nonstandard build configurations.","status":"published","published":"2021-06-16T18:15:00Z","modified":"2026-04-22T12:55:41.669757Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T15:54:27.870979Z"},{"id":"USN-5194-1","title":"olm vulnerability","description":"Denis Kasak discovered that Olm was not verifying the length of input being\nprocessed by the olm_pk_decrypt module, which introduced a stack-based buffer\noverflow vulnerability to the library. An attacker could use this to\ncause a denial of service (application crash) or possibly execute arbitrary code.\n","status":"published","published":"2021-12-15T13:45:51Z","modified":"2026-04-22T10:20:02.856443Z","updated_at":"2026-11-02T16:58:15.683829Z"}]}}