{"id":"CVE-2026-63495","aliases":["EUVD-2026-63503","GHSA-qx89-wf2v-vgmx","RHSA-2026:41176","UBUNTU-CVE-2026-63495"],"status":"published","title":"Libevent: Unbounded memory accumulation in WebSocket server via fragmented frames","description":"Libevent is an event notification library. From 2.2.0-alpha-dev until 2.2.2-alpha, the libevent WebSocket server in ws.c accumulates fragmented frames in evws-\u003eincomplete_frames without enforcing a total message-size limit. An unauthenticated remote client can repeatedly send fragmented WebSocket frames below WS_MAX_RECV_FRAME_SZ with FIN=0, causing the evbuffer to grow without bound until the process or host exhausts memory. This issue is fixed in version 2.2.2-alpha.","severity":{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00609,"percentile":0.49681,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-400","CWE-770"],"published":"2026-08-20T17:49:16Z","modified":"2026-10-28T11:17:06Z","fixes":[{"ecosystem":"Red Hat:hummingbird:1","package":"libevent","fixed_in":["0:2.1.12-19.hum1"],"sources":["osv"]},{"ecosystem":"Red Hat:hummingbird:1","package":"libevent-devel","fixed_in":["0:2.1.12-19.hum1"],"sources":["osv"]},{"ecosystem":"Red Hat:hummingbird:1","package":"libevent-doc","fixed_in":["0:2.1.12-19.hum1"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Red Hat:hummingbird:1","package":"libevent","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0:2.1.12-19.hum1"}]}]},{"source":"osv","ecosystem":"Red Hat:hummingbird:1","package":"libevent-devel","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0:2.1.12-19.hum1"}]}]},{"source":"osv","ecosystem":"Red Hat:hummingbird:1","package":"libevent-doc","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0:2.1.12-19.hum1"}]}]}],"products":[{"vendor":"libevent","product":"libevent"}],"references":[{"url":"https://github.com/libevent/libevent/security/advisories/GHSA-qx89-wf2v-vgmx","tags":["x_refsource_CONFIRM","exploit","advisory","article"]},{"url":"https://github.com/libevent/libevent/commit/291c4d1cd75695e898030ebd5c4ddf26c094077b","tags":["x_refsource_MISC","fix","article"]},{"url":"https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha","tags":["x_refsource_MISC","web","article"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63495.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63495","tags":["advisory"]},{"url":"https://access.redhat.com/errata/RHSA-2026:41176","tags":["advisory"]},{"url":"https://images.redhat.com/","tags":["article"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-63495","tags":["report"]},{"url":"https://access.redhat.com/security/updates/classification/","tags":["article"]},{"url":"https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_41176.json","tags":["advisory"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2520659","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-63495","tags":["advisory","report"]},{"url":"https://ubuntu.com/security/CVE-2026-63495","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-63495","title":"Libevent: Unbounded memory accumulation in WebSocket server via fragmented frames","description":"Libevent is an event notification library. From 2.2.0-alpha-dev until 2.2.2-alpha, the libevent WebSocket server in ws.c accumulates fragmented frames in evws-\u003eincomplete_frames without enforcing a total message-size limit. An unauthenticated remote client can repeatedly send fragmented WebSocket frames below WS_MAX_RECV_FRAME_SZ with FIN=0, causing the evbuffer to grow without bound until the process or host exhausts memory. This issue is fixed in version 2.2.2-alpha.","status":"published","published":"2026-08-20T17:49:16.79Z","modified":"2026-08-20T19:17:04.616Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-400","CWE-770"],"updated_at":"2026-11-02T14:19:55.914391Z"}],"euvd":[{"id":"EUVD-2026-63503","description":"Libevent is an event notification library. From 2.2.0-alpha-dev until 2.2.2-alpha, the libevent WebSocket server in ws.c accumulates fragmented frames in evws-\u003eincomplete_frames without enforcing a total message-size limit. An unauthenticated remote client can repeatedly send fragmented WebSocket frames below WS_MAX_RECV_FRAME_SZ with FIN=0, causing the evbuffer to grow without bound until the process or host exhausts memory. This issue is fixed in version 2.2.2-alpha.","status":"published","published":"2026-08-20T17:49:16Z","modified":"2026-08-20T19:17:04Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T18:01:38.846525Z"}],"nvd":[{"id":"CVE-2026-63495","description":"Libevent is an event notification library. From 2.2.0-alpha-dev until 2.2.2-alpha, the libevent WebSocket server in ws.c accumulates fragmented frames in evws-\u003eincomplete_frames without enforcing a total message-size limit. An unauthenticated remote client can repeatedly send fragmented WebSocket frames below WS_MAX_RECV_FRAME_SZ with FIN=0, causing the evbuffer to grow without bound until the process or host exhausts memory. This issue is fixed in version 2.2.2-alpha.","status":"published","published":"2026-08-20T18:16:37.04Z","modified":"2026-10-26T10:10:00.14Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-400","CWE-770"],"updated_at":"2026-11-02T14:12:40.302911Z"}],"osv":[{"id":"CVE-2026-63495","title":"Libevent: Unbounded memory accumulation in WebSocket server via fragmented frames","description":"Libevent is an event notification library. From 2.2.0-alpha-dev until 2.2.2-alpha, the libevent WebSocket server in ws.c accumulates fragmented frames in evws-\u003eincomplete_frames without enforcing a total message-size limit. An unauthenticated remote client can repeatedly send fragmented WebSocket frames below WS_MAX_RECV_FRAME_SZ with FIN=0, causing the evbuffer to grow without bound until the process or host exhausts memory. This issue is fixed in version 2.2.2-alpha.","status":"published","published":"2026-08-20T17:49:16.79Z","modified":"2026-10-28T11:17:06.764303713Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-400","CWE-770"],"updated_at":"2026-11-02T15:45:13.306117Z"},{"id":"RHSA-2026:41176","title":"Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update","status":"published","published":"2026-08-28T10:07:58Z","modified":"2026-10-06T10:31:29.492222409Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:53:20.491441Z"},{"id":"UBUNTU-CVE-2026-63495","description":"Libevent is an event notification library. From 2.2.0-alpha-dev until 2.2.2-alpha, the libevent WebSocket server in ws.c accumulates fragmented frames in evws-\u003eincomplete_frames without enforcing a total message-size limit. An unauthenticated remote client can repeatedly send fragmented WebSocket frames below WS_MAX_RECV_FRAME_SZ with FIN=0, causing the evbuffer to grow without bound until the process or host exhausts memory. This issue is fixed in version 2.2.2-alpha.","status":"withdrawn","published":"2026-08-20T18:16:00Z","modified":"2026-09-24T07:30:36.401322575Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T16:56:43.630667Z"}]}}