{"id":"CVE-2026-121289","kind":"vulnerability","aliases":["CVE-2026-121289"],"related":[],"title":"Arista EOS: crafted packet crashes the BGP agent (stack buffer overflow), code execution possible","description":"On affected platforms running Arista EOS with BGP configured, a specially crafted packet can cause the BGP agent to crash.\n\nSuccessful exploitation causes the BGP agent process to terminate, resulting in the loss of all BGP sessions on the affected device and possible disruption to network routing until the process recovers. Due to the nature of the vulnerability, it may also be possible for a sophisticated attacker to achieve arbitrary code execution, which could compromise the confidentiality and integrity of the affected system.","summary":"Arista Security Advisory 0208: on EOS with BGP configured and the multi-agent routing protocol model in use, a specially crafted packet can crash the BGP agent (stack-based buffer overflow, CWE-121), dropping all BGP sessions. Arista says a sophisticated attacker may also achieve arbitrary code execution; that is stated as possible, not demonstrated. Reported by Joshua Foote of JP Morgan Chase; Arista is not aware of malicious exploitation.","severity":"critical","cvss":9.8,"epss":null,"exploited":false,"exploited_at":null,"products":[{"name":"EOS","fixed":["4.37.0F","4.36.3M","4.35.7M","4.34.9M","4.33.11M"],"affected":"<= 4.36.2F","ecosystem":"vendor"}],"ecosystems":[],"tags":["arista-eos","bgp","infrastructure","network-infrastructure","self-hosted"],"not_affected_if":["no-bgp-configured","ribd-routing-model"],"how_to_check":"Exposed only if BOTH hold: BGP is running (`show ip bgp summary` does not say '% BGP is not running') AND `show running-config all | inc service routing protocols` returns 'service routing protocols model multi-agent' (model ribd = not exposed). Then compare `show version` with the affected list. IoC: `grep \"PROCESS_TERMINATED: 'Bgp'\" /var/log/eos` from bash, or the ProcMgr 'Bgp ... status=-11 has terminated' line in show logging.","fix":"Upgrade to 4.37.0F or later, 4.36.3M, 4.35.7M, 4.34.9M or 4.33.11M (or later in the same train). No hotfix. Workaround if you do not use the Tunnel Encapsulation Attribute: 'neighbor default received attribute discard 23'. Mitigation: TCP-AO authentication on BGP peers.","status":"open","published_at":"2026-11-10T20:18:54+00:00","first_seen_at":"2026-11-10T20:46:03+00:00","triaged_at":"2026-11-10T20:47:17+00:00","updated_at":"2026-11-10T20:51:02+00:00","category":"infrastructure","confidence":0.9,"triage":{"at":"2026-11-10T20:47:17Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"Arista EOS: crafted packet crashes BGP agent, dropping all BGP sessions","impact":"high","summary":"A specially crafted packet can crash the BGP agent on Arista EOS devices that have BGP configured, dropping every BGP session until the process recovers. The advisory also says a sophisticated attacker may be able to run arbitrary code on the device.","audience":"businesses","category":"infrastructure","nicknames":[],"who_cares":["arista-eos","bgp","network-infrastructure"],"confidence":0.6,"fix_status":"unknown","needs_auth":"unknown","worst_case":"BGP agent crashes, dropping routing; possible code execution","analyst_note":"Find the affected EOS version ranges and fixed releases in the Arista security advisory for CVE-2026-121289 and confirm whether the code execution claim applies.","how_to_check":"- Check whether BGP is configured on the device (for example with `show running-config | include router bgp`).\n- Compare the running EOS version against the affected ranges in the Arista advisory; the sources do not list them.","plain_action":"","product_name":"","needs_analyst":true,"not_affected_if":["no-bgp-configured"],"who_is_affected":"Network devices running Arista EOS with BGP configured are affected. Devices without BGP configured are not exposed through this path. The sources do not list affected EOS versions or whether a fix exists yet.","user_interaction":"no","product_ecosystem":"","needs_special_setup":"yes","severity_if_unknown":"critical"},"cost_usd":0.000726,"input_tokens":4619,"output_tokens":529,"severity_before":"critical"},"analyst_status":"done","analyst_note":"Find the affected EOS version ranges and fixed releases in the Arista security advisory for CVE-2026-121289 and confirm whether the code execution claim applies.","search":"'-121':67B '-121289':17A,20A '-2026':16A,19A '0208':36B 'achiev':79B,173C 'advisori':35B 'affect':106C,144C,186C 'agent':8A,46B,60B,122C,130C 'also':78B,165C 'arbitrari':80B,174C 'arista':1A,23B,33B,72B,98B,109C 'arista-eo':22B 'attack':76B,171C 'awar':101B 'base':63B 'bgp':7A,25B,40B,59B,70B,112C,121C,129C,140C 'buffer':10A,64B 'caus':119C,127C 'chase':97B 'code':12A,81B,175C 'compromis':179C 'confidenti':181C 'configur':41B,113C 'could':178C 'craft':3A,54B,116C 'crash':5A,57B,124C 'cve':15A,18A 'cwe':66B 'demonstr':89B 'devic':145C 'disrupt':148C 'drop':68B 'due':156C 'eo':2A,24B,38B,110C 'eos':21A 'execut':13A,82B,176C 'exploit':104B,126C 'foot':93B 'host':32B 'infrastructur':26B,29B 'integr':183C 'joshua':92B 'jp':95B 'loss':137C 'malici':103B 'may':77B,164C 'model':49B 'morgan':96B 'multi':45B 'multi-ag':44B 'natur':159C 'network':28B,150C 'network-infrastructur':27B 'overflow':11A,65B 'packet':4A,55B,117C 'platform':107C 'possibl':14A,87B,147C,167C 'process':131C,154C 'protocol':48B 'recov':155C 'report':90B 'result':134C 'rout':47B,151C 'run':108C 'say':73B 'secur':34B 'self':31B 'self-host':30B 'session':71B,141C 'sophist':75B,170C 'special':53B,115C 'stack':9A,62B 'stack-bas':61B 'state':85B 'success':125C 'system':187C 'termin':133C 'use':51B 'vulner':162C","nicknames":[],"mitigations":[],"who_affected":"Arista EOS switches and routers (7000-series families, CloudEOS, cEOS-lab, vEOS-lab, CloudVision eXchange) running BGP with the multi-agent routing protocol model, on 4.36.2F and below, 4.35.6M and below, 4.34.8M and below, 4.33.10M and below, and all end-of-support trains from 4.25.1F. Devices without BGP, or on the ribd model, are not exposed. Wi-Fi APs, CloudVision Portal, NetVisor, VeloCloud and other listed products are not affected.","tier":"B","verified":{"fix":{"at":"2026-11-10T20:51:02Z","by":"analyst","doc":"https://www.arista.com/en/support/advisories-notices/security-advisory/25030-security-advisory-0208","run_id":2713},"products":{"at":"2026-11-10T20:51:02Z","by":"analyst","doc":"https://www.arista.com/en/support/advisories-notices/security-advisory/25030-security-advisory-0208","run_id":2713},"mitigations":{"at":"2026-11-10T20:51:02Z","by":"analyst","doc":"https://www.arista.com/en/support/advisories-notices/security-advisory/25030-security-advisory-0208","run_id":2713},"how_to_check":{"at":"2026-11-10T20:51:02Z","by":"analyst","doc":"https://www.arista.com/en/support/advisories-notices/security-advisory/25030-security-advisory-0208","run_id":2713},"who_affected":{"at":"2026-11-10T20:51:02Z","by":"analyst","doc":"https://www.arista.com/en/support/advisories-notices/security-advisory/25030-security-advisory-0208","run_id":2713}},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":["eos"],"ptokens":["eos"],"labels":["aristaeos","bgp","critical","infrastructure","networkinfrastructure","selfhosted"],"campaign_type":null,"search_a":"'-121289':17A,20A '-2026':16A,19A 'agent':8A 'arista':1A 'bgp':7A 'buffer':10A 'code':12A 'craft':3A 'crash':5A 'cve':15A,18A 'eo':2A 'eos':21A 'execut':13A 'overflow':11A 'packet':4A 'possibl':14A 'stack':9A","search_b":"'-121':67B '0208':36B 'achiev':79B 'advisori':35B 'agent':46B,60B 'also':78B 'arbitrari':80B 'arista':23B,33B,72B,98B 'arista-eo':22B 'attack':76B 'awar':101B 'base':63B 'bgp':25B,40B,59B,70B 'buffer':64B 'chase':97B 'code':81B 'configur':41B 'craft':54B 'crash':57B 'cwe':66B 'demonstr':89B 'drop':68B 'eo':24B,38B 'execut':82B 'exploit':104B 'foot':93B 'host':32B 'infrastructur':26B,29B 'joshua':92B 'jp':95B 'malici':103B 'may':77B 'model':49B 'morgan':96B 'multi':45B 'multi-ag':44B 'network':28B 'network-infrastructur':27B 'overflow':65B 'packet':55B 'possibl':87B 'protocol':48B 'report':90B 'rout':47B 'say':73B 'secur':34B 'self':31B 'self-host':30B 'session':71B 'sophist':75B 'special':53B 'stack':62B 'stack-bas':61B 'state':85B 'use':51B","search_c":"'achiev':173C 'affect':106C,144C,186C 'agent':122C,130C 'also':165C 'arbitrari':174C 'arista':109C 'attack':171C 'bgp':112C,121C,129C,140C 'caus':119C,127C 'code':175C 'compromis':179C 'confidenti':181C 'configur':113C 'could':178C 'craft':116C 'crash':124C 'devic':145C 'disrupt':148C 'due':156C 'eo':110C 'execut':176C 'exploit':126C 'integr':183C 'loss':137C 'may':164C 'natur':159C 'network':150C 'packet':117C 'platform':107C 'possibl':147C,167C 'process':131C,154C 'recov':155C 'result':134C 'rout':151C 'run':108C 'session':141C 'sophist':170C 'special':115C 'success':125C 'system':187C 'termin':133C 'vulner':162C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-10T20:18:54+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"psirt@arista.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-121289","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-121289","severity":null,"published_at":"2026-11-10T20:18:54+00:00","modified_at":"2026-11-10T20:18:54+00:00","first_seen_at":"2026-11-10T20:46:03+00:00","fetched_at":"2026-11-10T20:46:03+00:00","note":null},{"source":"analyst","external_id":"CVE-2026-121289:2713","url":"https://www.arista.com/en/support/advisories-notices/security-advisory/25030-security-advisory-0208","severity":null,"published_at":"2026-11-10T20:51:02+00:00","modified_at":"2026-11-10T20:51:02+00:00","first_seen_at":"2026-11-10T20:51:02+00:00","fetched_at":"2026-11-10T20:51:02+00:00","note":"Read Arista SA 0208 (primary). Stack-based buffer overflow (CWE-121); exposure needs BGP + multi-agent model. RCE is the vendor's 'may be possible' for a sophisticated attacker, not demonstrated. No known exploitation per Arista. Social search skipped (brand-new, not needed).","cites":["https://www.arista.com/en/support/advisories-notices/security-advisory/25030-security-advisory-0208"]}],"documents":[{"id":118298,"url":"https://www.arista.com/en/support/advisories-notices/security-advisory/25030-security-advisory-0208","title":"Arista Security Advisory 0208 (CVE-2026-121289)","kind":"advisory","source":"analyst","publisher":null,"text":null,"published_at":null,"relation":"advisory","confidence":null,"note":null}],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}