{"id":"CVE-2026-76491","kind":"vulnerability","aliases":["CVE-2026-76491"],"related":[],"title":"Cisco Expressway: reachable assertions let remote requests crash the appliance","description":"As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco Expressway Series software engineering team has conducted a comprehensive internal security review. This review resulted in software hardening releases that address multiple internally discovered vulnerabilities.  \r\n\r\nThe vulnerabilities tracked by CVE-2026-76491 are related to issues concerning reachable assertions that are grouped under the Common Weakness Enumeration (CWE) Base CWE-617.","summary":"Cisco Expressway Series contains reachable assertion failures (CWE-617) found in an internal security review, which Cisco fixed in hardening releases. An attacker who can send crafted traffic can trigger an assertion that stops the service, causing denial of service.","severity":"high","cvss":7.5,"epss":0.00263,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["cisco-expressway","infrastructure","network-appliance","video-collaboration"],"not_affected_if":["not-running-expressway"],"how_to_check":"- unknown","fix":"- Upgrade Cisco Expressway to the fixed release named in Cisco's advisory (version unknown from the sources)","status":"open","published_at":"2026-10-21T17:19:08+00:00","first_seen_at":"2026-10-23T21:57:29+00:00","triaged_at":"2026-10-25T03:16:31+00:00","updated_at":"2026-10-25T03:16:31+00:00","category":"infrastructure","confidence":0.5,"triage":{"at":"2026-10-25T03:16:31Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade Cisco Expressway to the fixed release named in Cisco's advisory (version unknown from the sources)","reach":"network","title":"Cisco Expressway: reachable assertions let remote requests crash the appliance","impact":"medium","summary":"Cisco Expressway Series contains reachable assertion failures (CWE-617) found in an internal security review, which Cisco fixed in hardening releases. An attacker who can send crafted traffic can trigger an assertion that stops the service, causing denial of service.","category":"infrastructure","nicknames":[],"who_cares":["cisco-expressway","video-collaboration","network-appliance"],"confidence":0.5,"needs_auth":"unknown","worst_case":"Service crashes via reachable assertion, denying availability of the appliance","analyst_note":"Find the affected and fixed Expressway versions and the triggering conditions in Cisco's advisory, linked from the NVD entry at https://nvd.nist.gov/vuln/detail/CVE-2026-76491.","how_to_check":"- unknown","needs_analyst":true,"not_affected_if":["not-running-expressway"],"who_is_affected":"Organizations running Cisco Expressway Series appliances, which handle video and collaboration traffic at the network edge. The sources do not name the affected versions or which features must be enabled, so check Cisco's advisory before assuming exposure. Teams not running Expressway can skip it.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000606,"input_tokens":3416,"output_tokens":528,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-2026':12A,15A,112C '-617':35B,132C '-76491':13A,16A,113C 'address':102C 'applianc':10A,23B 'assert':4A,32B,58B,120C 'attack':49B 'base':130C 'caus':63B 'cisco':1A,18B,27B,43B,70C,81C 'cisco-expressway':17B 'collabor':26B 'commit':73C 'common':126C 'comprehens':90C 'concern':118C 'conduct':88C 'contain':30B 'craft':53B 'crash':8A 'cve':11A,14A,111C 'cwe':34B,129C,131C 'denial':64B 'discov':105C 'engin':85C 'enumer':128C 'expressway':2A,19B,28B,82C 'failur':33B 'fix':44B 'found':36B 'group':123C 'harden':46B,99C 'infrastructur':20B 'intern':39B,91C,104C 'issu':117C 'let':5A 'multipl':103C 'network':22B 'network-appli':21B 'ongo':72C 'part':68C 'proactiv':75C 'product':78C 'qualiti':79C 'reachabl':3A,31B,119C 'relat':115C 'releas':47B,100C 'remot':6A 'request':7A 'result':96C 'review':41B,93C,95C 'secur':40B,76C,92C 'send':52B 'seri':29B,83C 'servic':62B,66B 'softwar':84C,98C 'stop':60B 'team':86C 'track':109C 'traffic':54B 'trigger':56B 'video':25B 'video-collabor':24B 'vulner':106C,108C 'weak':127C","nicknames":[],"mitigations":[],"who_affected":"Organizations running Cisco Expressway Series appliances, which handle video and collaboration traffic at the network edge. The sources do not name the affected versions or which features must be enabled, so check Cisco's advisory before assuming exposure. Teams not running Expressway can skip it.","tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-21T17:19:08+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cvss_by":"psirt@cisco.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-76491","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-76491","severity":null,"published_at":"2026-10-21T17:19:08+00:00","modified_at":"2026-10-22T14:17:47+00:00","first_seen_at":"2026-10-23T21:57:29+00:00","fetched_at":"2026-10-23T22:29:01+00:00","note":null},{"source":"epss","external_id":"CVE-2026-76491","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-76491","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-24T13:15:54+00:00","fetched_at":"2026-10-24T13:15:54+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}