{"id":"CVE-2026-86696","kind":"vulnerability","aliases":["CVE-2026-86696"],"related":[],"title":"esaml: unsigned logout requests can crash Erlang node via atom exhaustion","description":"Allocation of Resources Without Limits or Throttling vulnerability in esaml in dropbox esaml allows an unauthenticated attacker to exhaust the Erlang VM atom table and crash the node via unsigned LogoutResponse messages.\n\nesaml:status_code_map/1 in src/esaml.erl maps any StatusCode value it does not recognize to an atom with list_to_atom/1 on the last colon-separated segment of the URN. esaml_sp:validate_logout_response/2 verifies a signature only when the message carries one, so an unsigned LogoutResponse posted to the single-logout endpoint reaches esaml:decode_logout_response/1 and mints one permanent atom per distinct status value. Atoms are never reclaimed and the VM caps the atom table at about one million entries, so an attacker who posts that many distinct values aborts the node.\n\nThis issue affects esaml: from 0.1.0 onward.","summary":"esaml, a SAML service provider library for Erlang, turns each distinct unrecognized status value in an unsigned LogoutResponse into a permanent atom. An unauthenticated attacker can exhaust the Erlang VM atom table and crash the node.","severity":"high","cvss":8.2,"epss":0.00438,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["elixir","erlang","package","saml","single-sign-on"],"not_affected_if":["logout-endpoint-not-exposed","no-esaml-dependency"],"how_to_check":"- Check whether the project depends on esaml (`rebar.lock`, `rebar.config`, or `mix.lock` for Elixir projects) and note the version in use\n- Check whether the single-logout endpoint is exposed to the internet, since it accepts unsigned LogoutResponse messages","fix":"- Upgrade esaml to a version that fixes this issue; the sources do not name the fixed version, so unknown\n- Until patched, restrict or rate-limit the single-logout endpoint at the proxy or load balancer","status":"open","published_at":"2026-10-22T09:17:16+00:00","first_seen_at":"2026-10-23T21:57:30+00:00","triaged_at":"2026-10-25T03:03:45+00:00","updated_at":"2026-10-25T03:03:45+00:00","category":"package","confidence":0.7,"triage":{"at":"2026-10-25T03:03:45Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade esaml to a version that fixes this issue; the sources do not name the fixed version, so unknown\n- Until patched, restrict or rate-limit the single-logout endpoint at the proxy or load balancer","reach":"internet","title":"esaml: unsigned logout requests can crash Erlang node via atom exhaustion","impact":"high","summary":"esaml, a SAML service provider library for Erlang, turns each distinct unrecognized status value in an unsigned LogoutResponse into a permanent atom. An unauthenticated attacker can exhaust the Erlang VM atom table and crash the node.","category":"package","nicknames":[],"who_cares":["erlang","elixir","saml","single-sign-on"],"confidence":0.7,"needs_auth":"no","worst_case":"unauthenticated attacker crashes the Erlang node by exhausting atoms","analyst_note":"Find the fixed esaml version and the patch commit at the esaml repository (github.com/dropbox/esaml) and confirm the affected version range.","how_to_check":"- Check whether the project depends on esaml (`rebar.lock`, `rebar.config`, or `mix.lock` for Elixir projects) and note the version in use\n- Check whether the single-logout endpoint is exposed to the internet, since it accepts unsigned LogoutResponse messages","needs_analyst":true,"not_affected_if":["no-esaml-dependency","logout-endpoint-not-exposed"],"who_is_affected":"Applications that use esaml as a SAML service provider and expose its single-logout endpoint to untrusted clients are exposed, because unsigned LogoutResponse messages reach the atom-creating code path. Services that do not use esaml, or that do not expose the logout endpoint publicly, are less exposed. The sources do not say whether any particular deployment setting blocks the path.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000691,"input_tokens":3564,"output_tokens":670,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-2026':13A,16A '-86696':14A,17A '0.1.0':196C 'abort':188C 'affect':193C 'alloc':61C 'allow':74C 'atom':10A,46B,55B,83C,109C,158C,163C,172C 'atom/1':113C 'attack':49B,77C,181C 'cap':170C 'carri':136C 'code':95C 'colon':118C 'colon-separ':117C 'crash':6A,58B,86C 'cve':12A,15A 'decod':151C 'distinct':35B,160C,186C 'dropbox':72C 'elixir':18B 'endpoint':148C 'entri':178C 'erlang':7A,19B,32B,53B,81C 'esaml':1A,25B,70C,73C,93C,124C,150C,194C 'exhaust':11A,51B,79C 'issu':192C 'last':116C 'librari':30B 'limit':65C 'list':111C 'logout':3A,127C,147C,152C 'logoutrespons':42B,91C,141C 'mani':185C 'map':99C 'map/1':96C 'messag':92C,135C 'million':177C 'mint':155C 'never':165C 'node':8A,60B,88C,190C 'one':137C,156C,176C 'onward':197C 'packag':20B 'per':159C 'perman':45B,157C 'post':142C,183C 'provid':29B 'reach':149C 'reclaim':166C 'recogn':106C 'request':4A 'resourc':63C 'response/1':153C 'response/2':128C 'saml':21B,27B 'segment':120C 'separ':119C 'servic':28B 'sign':24B 'signatur':131C 'singl':23B,146C 'single-logout':145C 'single-sign-on':22B 'sp':125C 'src/esaml.erl':98C 'status':37B,94C,161C 'statuscod':101C 'tabl':56B,84C,173C 'throttl':67C 'turn':33B 'unauthent':48B,76C 'unrecogn':36B 'unsign':2A,41B,90C,140C 'urn':123C 'valid':126C 'valu':38B,102C,162C,187C 'verifi':129C 'via':9A,89C 'vm':54B,82C,169C 'vulner':68C 'without':64C","nicknames":[],"mitigations":[],"who_affected":"Applications that use esaml as a SAML service provider and expose its single-logout endpoint to untrusted clients are exposed, because unsigned LogoutResponse messages reach the atom-creating code path. Services that do not use esaml, or that do not expose the logout endpoint publicly, are less exposed. The sources do not say whether any particular deployment setting blocks the path.","tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-22T09:17:16+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/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":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-86696","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-86696","severity":null,"published_at":"2026-10-22T09:17:16+00:00","modified_at":"2026-10-22T16:58:51+00:00","first_seen_at":"2026-10-23T21:57:30+00:00","fetched_at":"2026-10-23T22:29:02+00:00","note":null},{"source":"epss","external_id":"CVE-2026-86696","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-86696","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-24T07:15:51+00:00","fetched_at":"2026-10-24T07:15:51+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"}