{"id":"CVE-2026-26209","title":"cbor2: cbor2: Denial of Service due to uncontrolled recursion via crafted CBOR payloads (CVE-2026-26209)","summary":"A flaw was found in cbor2, a library for encoding and decoding Concise Binary Object Representation (CBOR) data. A remote attacker can exploit this vulnerability by sending a specially crafted CBOR payload containing deeply nested structur…","severity":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cvssSource":"vendor","cwe":"CWE-770","vendor":"Red Hat","product":"Red Hat Enterprise Linux AI (RHEL AI) 3","affected":["ai_inference_server","ansible_automation_platform 2","enterprise_linux_ai_rhel_ai 3","openshift_ai_rhoai","ai_inference_server 3.2","ai_inference_server 3.3"],"patched":["ai_inference_server 3.2","ai_inference_server 3.3"],"published":"2026-03-23","updated":"2026-09-21","sourceUpdated":"2026-09-21T17:22:42+00:00","source":"CSAF","sourceUrl":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-26209.json","references":[{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-26209.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-26209"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2450422"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-26209"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-26209"},{"url":"https://github.com/agronholm/cbor2/commit/e61a5f365ba610d5907a0ae1bc72769bba34294b"},{"url":"https://github.com/agronholm/cbor2/pull/275"},{"url":"https://github.com/agronholm/cbor2/releases/tag/5.9.0"},{"url":"https://github.com/agronholm/cbor2/security/advisories/GHSA-3c37-wwvx-h642"},{"url":"https://access.redhat.com/errata/RHSA-2026:19724"},{"url":"https://access.redhat.com/errata/RHSA-2026:19725"},{"url":"https://access.redhat.com/errata/RHSA-2026:16030"},{"url":"https://access.redhat.com/errata/RHSA-2026:16009"},{"url":"https://access.redhat.com/errata/RHSA-2026:16174"},{"url":"https://github.com/agronholm/cbor2"}],"tags":["csaf","vex","red-hat","osv","pip","score-dispute"],"epss":0.00649,"epssPercentile":0.48869,"aliases":["GHSA-3c37-wwvx-h642","PYSEC-2026-2123"],"ecosystem":"pip","scores":{"vendor":5.5,"osv":7.5},"ingestedAt":"2026-07-13T18:57:51.809Z","slug":"CVE-2026-26209","body":"## Overview\n\nA flaw was found in cbor2, a library for encoding and decoding Concise Binary Object Representation (CBOR) data. A remote attacker can exploit this vulnerability by sending a specially crafted CBOR payload containing deeply nested structures. This can cause the application to crash due to uncontrolled recursion, leading to a complete Denial of Service (DoS) for the affected application.\n\n## Vendor advisories\n\n- **RHSA-2026:19724** · Red Hat · fixed in: Red Hat AI Inference Server 3.2 · released 2026-05-20 · [advisory](https://access.redhat.com/errata/RHSA-2026:19724)\n- **RHSA-2026:19725** · Red Hat · fixed in: Red Hat AI Inference Server 3.2 · released 2026-05-20 · [advisory](https://access.redhat.com/errata/RHSA-2026:19725)\n- **RHSA-2026:16030** · Red Hat · fixed in: Red Hat AI Inference Server 3.3 · released 2026-05-11 · [advisory](https://access.redhat.com/errata/RHSA-2026:16030)\n- **RHSA-2026:16009** · Red Hat · fixed in: Red Hat AI Inference Server 3.3 · released 2026-05-11 · [advisory](https://access.redhat.com/errata/RHSA-2026:16009)\n- **RHSA-2026:16174** · Red Hat · fixed in: Red Hat AI Inference Server 3.3 · released 2026-05-12 · [advisory](https://access.redhat.com/errata/RHSA-2026:16174)\n- **Red Hat VEX** · Moderate · affected: Red Hat AI Inference Server, Red Hat Ansible Automation Platform 2, Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat OpenShift AI (RHOAI) · no fix planned: Red Hat AI Inference Server, Red Hat Ansible Automation Platform 2, Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat OpenShift AI (RHOAI) · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-26209.json)\n\n**cbor2: cbor2: Denial of Service due to uncontrolled recursion via crafted CBOR payloads** — rated Moderate by Red Hat. Released 2026-03-23, updated 2026-09-21.\n\nAffected:\n\n- Red Hat AI Inference Server\n- Red Hat Ansible Automation Platform 2\n- Red Hat Enterprise Linux AI (RHEL AI) 3\n- Red Hat OpenShift AI (RHOAI)\n\nFixed:\n\n- Red Hat AI Inference Server 3.2\n- Red Hat AI Inference Server 3.3\n\nNo fix planned:\n\n- Red Hat AI Inference Server\n- Red Hat Ansible Automation Platform 2\n- Red Hat Enterprise Linux AI (RHEL AI) 3\n- Red Hat OpenShift AI (RHOAI)\n\n## Remediation\n\nFor more information visit https://access.redhat.com/errata/RHSA-2026:19724 https://access.redhat.com/errata/RHSA-2026:19724\nFor more information visit https://access.redhat.com/errata/RHSA-2026:19725 https://access.redhat.com/errata/RHSA-2026:19725\nFor more information visit https://access.redhat.com/errata/RHSA-2026:16030 https://access.redhat.com/errata/RHSA-2026:16030\n\n## Package advisory (CVE-2026-26209)\n\nAffected packages:\n\n- `cbor2 < 5.9.0`\n\nPatched in:\n\n- `cbor2 5.9.0`\n\nSource: https://osv.dev/vulnerability/GHSA-3c37-wwvx-h642","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":208965,"id":"CVE-2026-26209","ts":1790062302801,"field":"cvss","old":"7.5","new":"5.5"},{"seq":208964,"id":"CVE-2026-26209","ts":1790062302801,"field":"severity","old":"high","new":"medium"}]}