Unbounded atom creation while parsing SAML messages in esaml allows atom table exhaustion

{
  "id": "bf833c8932bc65f4244990338c58dd95f4a1bf4b0aed7887c6266f8b1dbc4c3f",
  "url": "https://osv.dev/vulnerability/EEF-CVE-2026-105270",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Unbounded atom creation while parsing SAML messages in esaml allows atom table exhaustion",
    "summary": "## Summary Allocation of Resources Without Limits or Throttling vulnerability in `esaml_binding` in dropbox esaml allows an unauthenticated attacker to exhaust the Erlang VM atom table and crash the node via a crafted `SAMLResponse`. `esaml_binding:decode_response/2` parses the decoded `SAMLResponse` with `xmerl_scan:string/2`, which interns every element name, attribute name, and namespace prefix it reads as a permanent atom. The SAML consume (ACS) and single-logout endpoints call it on unauthenticated requests before any signature check, so one well-formed document with thousands of distinct names mints thousands of atoms while staying inside the 128 KB request body limit. Atoms are never reclaimed and the VM caps the atom table at about one million entries, so a few dozen requests abort the node. This issue affects esaml: from 0.1.0 onward. ## Details **1. Input.** The SAML consume (ACS) and single-logout endpoints in `esaml_cowboy` read the request body, capped at 128 KB, and pass the `SAMLResponse` form field to `esaml_binding:decode_response/2`. Both the DEFLATE clause and the default clause end in `xmerl_scan:string/2` with `namespace_conformant` set. **2. Interning.** `xmerl_scan` converts every element name, attribute name, and namespace prefix it tokenizes into an atom with `list_to_atom/1`, and the same happens for each namespace local name in `expanded_name/4`. A well-formed document with many distinct names therefore mints one permanent atom per name. Repetitive ",
    "evidence": "osv:EEF-CVE-2026-105270",
    "products": [
      {
        "name": {
          "value": "esaml",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "3.0.1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "3.1.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "3.2.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "3.3.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "3.4.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "3.5.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "3.6.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "3.6.1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "3.7.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "4.0.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "4.1.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "4.2.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "4.3.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "4.4.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "4.5.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "4.6.0",
            "evidence": "/affected/0/versions"
          }
        ]
      }
    ],
    "severity": "high",
    "structured": {
      "id": "EEF-CVE-2026-105270",
      "aliases": [
        "CVE-2026-105270",
        "EEF-CVE-2026-105270"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0.1.0"
                }
              ]
            }
          ],
          "package": {
            "name": "esaml",
            "purl": "pkg:hex/esaml",
            "ecosystem": "Hex"
          },
          "versions": [
            "3.0.1",
            "3.1.0",
            "3.2.0",
            "3.3.0",
            "3.4.0",
            "3.5.0",
            "3.6.0",
            "3.6.1",
            "3.7.0",
            "4.0.0",
            "4.1.0",
            "4.2.0",
            "4.3.0",
            "4.4.0",
            "4.5.0",
            "4.6.0"
          ],
          "database_specific": {
            "source": "https://cna.erlef.org/osv/EEF-CVE-2026-105270.json"
          }
        },
        {
          "ranges": [
            {
              "repo": "https://github.com/arekinath/esaml",
              "type": "GIT",
              "events": [
                {
                  "introduced": "deeb84378d5c82153b470e99d24f77c38afca14a"
                }
              ]
            }
          ],
          "versions": [
            "v1.1",
            "v1.0",
            "v0.1"
          ],
          "database_specific": {
            "source": "https://cna.erlef.org/osv/EEF-CVE-2026-105270.json"
          }
        },
        {
          "ranges": [
            {
              "repo": "https://github.com/handnot2/esaml",
              "type": "GIT",
              "events": [
                {
                  "introduced": "deeb84378d5c82153b470e99d24f77c38afca14a"
                }
              ]
            }
          ],
          "versions": [
            "v4.2.0",
            "v3.6.1",
            "v4.1.0",
            "v4.0.0",
            "v3.6.0",
            "v3.5.0",
            "v3.4.0",
            "v3.3.0",
            "v3.2.0",
            "v3.1.0",
            "v3.0.1",
            "v3.0.0",
            "v2.1.0",
            "2.0.0",
            "v1.1",
            "v1.0",
            "v0.1"
          ],
          "database_specific": {
            "source": "https://cna.erlef.org/osv/EEF-CVE-2026-105270.json"
          }
        },
        {
          "ranges": [
            {
              "repo": "https://github.com/dropbox/esaml",
              "type": "GIT",
              "events": [
                {
                  "introduced": "deeb84378d5c82153b470e99d24f77c38afca14a"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://cna.erlef.org/osv/EEF-CVE-2026-105270.json"
          }
        }
      ],
      "modified": "2026-10-22T07:00:03.393920401Z",
      "provider": "osv",
      "references": [
        "https://cna.erlef.org/cves/CVE-2026-105270.html",
        "https://github.com/arekinath/esaml/commit/deeb84378d5c82153b470e99d24f77c38afca14a",
        "https://github.com/handnot2/esaml/commit/deeb84378d5c82153b470e99d24f77c38afca14a",
        "https://github.com/dropbox/esaml/commit/deeb84378d5c82153b470e99d24f77c38afca14a",
        "https://hex.pm/packages/esaml"
      ],
      "provider_metadata": {
        "cpe_ids": [
          "cpe:2.3:a:arekinath:esaml:*:*:*:*:*:*:*:*",
          "cpe:2.3:a:handnot2:esaml:*:*:*:*:*:*:*:*",
          "cpe:2.3:a:dropbox:esaml:*:*:*:*:*:*:*:*"
        ],
        "cwe_ids": [
          "CWE-770"
        ],
        "capec_ids": [
          "CAPEC-130"
        ]
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-105270",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 404579,
  "published_at": "2026-10-22T06:58:43.034+00:00"
}