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High

AshAdmin cookie reader matches names by substring, enabling actor/session shadowing from a sibling subdomain

Type: advisorySources: OSV

Reliance on Cookies without Validation and Integrity Checking vulnerability in ash-project ash_admin lets an attacker who controls a sibling subdomain rebind an admin's session to a different actor, tenant, or authorization mode. AshAdmin's client JavaScript read its state cookies (tenant, actor_resource, actor_primary_key, actor_action, actor_domain, actor_authorizing, actor_paused) by matching the cookie name with an unanchored regular expression (new RegExp(name + "=([^;]+)")) against the whole document.cookie. Any cookie whose name merely ends with the requested name therefore matches, and whichever is serialized first wins. Because cookies are shared across a registrable domain, a compromised sibling subdomain can set a shadowing cookie (for example xactor_authorizing) with Domain=.example.com that flows unvalidated into the admin's LiveSocket connect params. The fix matches cookie names by exact equality. This issue affects ash_admin: from 0.9.1 before 1.3.1.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-75757
Confirmed fixed CVEs
Not specified
Updated in this feed
3 Nov 2026, 13:16 UTC · Revision 1

Source evidence

AshAdmin cookie reader matches names by substring, enabling actor/session shadowing from a sibling subdomain

core-osv · Original source

Published 31 Aug 2026, 02:20 UTC

Reliance on Cookies without Validation and Integrity Checking vulnerability in ash-project ash_admin lets an attacker who controls a sibling subdomain rebind an admin's session to a different actor, tenant, or authorization mode. AshAdmin's client JavaScript read its state cookies (tenant, actor_resource, actor_primary_key, actor_action, actor_domain, actor_authorizing, actor_paused) by matching the cookie name with an unanchored regular expression (new RegExp(name + "=([^;]+)")) against the whole document.cookie. Any cookie whose name merely ends with the requested name therefore matches, and whichever is serialized first wins. Because cookies are shared across a registrable domain, a compromised sibling subdomain can set a shadowing cookie (for example xactor_authorizing) with Domain=.example.com that flows unvalidated into the admin's LiveSocket connect params. The fix matches cookie names by exact equality. This issue affects ash_admin: from 0.9.1 before 1.3.1.

osv:CVE-2026-75757
Complete source record
{
  "id": "9bbdd1d6a5ba917b2327c2041f0d907aa1080cb966c1844f2d64aacdecb548a5",
  "url": "https://osv.dev/vulnerability/CVE-2026-75757",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "AshAdmin cookie reader matches names by substring, enabling actor/session shadowing from a sibling subdomain",
    "summary": "Reliance on Cookies without Validation and Integrity Checking vulnerability in ash-project ash_admin lets an attacker who controls a sibling subdomain rebind an admin's session to a different actor, tenant, or authorization mode. AshAdmin's client JavaScript read its state cookies (tenant, actor_resource, actor_primary_key, actor_action, actor_domain, actor_authorizing, actor_paused) by matching the cookie name with an unanchored regular expression (new RegExp(name + \"=([^;]+)\")) against the whole document.cookie. Any cookie whose name merely ends with the requested name therefore matches, and whichever is serialized first wins. Because cookies are shared across a registrable domain, a compromised sibling subdomain can set a shadowing cookie (for example xactor_authorizing) with Domain=.example.com that flows unvalidated into the admin's LiveSocket connect params. The fix matches cookie names by exact equality. This issue affects ash_admin: from 0.9.1 before 1.3.1.",
    "evidence": "osv:CVE-2026-75757",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-75757",
      "aliases": [
        "CVE-2026-75757",
        "EEF-CVE-2026-75757",
        "GHSA-3259-55fp-w94j"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/ash-project/ash_admin",
              "type": "GIT",
              "events": [
                {
                  "introduced": "77a43cc4fa04cb59c38fc434568a35a38ecb995a"
                },
                {
                  "fixed": "e93a3408a85035e1f90275d02bc2470c96095e56"
                },
                {
                  "introduced": "9297612f82dc03585f65b9e1b0eba72a74b0751f"
                },
                {
                  "fixed": "91da87c1c23cd6199ba1b0a1c8849a4c605130cc"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "77a43cc4fa04cb59c38fc434568a35a38ecb995a"
                      },
                      {
                        "fixed": "e93a3408a85035e1f90275d02bc2470c96095e56"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0.9.1"
                      },
                      {
                        "fixed": "1.3.1"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "fixed": "e93a3408a85035e1f90275d02bc2470c96095e56"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v1.3.0",
            "v1.2.0",
            "v1.1.0",
            "v0.14.0",
            "v0.13.26",
            "v0.13.25",
            "v0.13.24",
            "v0.13.23",
            "v0.13.22",
            "v0.13.21",
            "v0.13.20",
            "v0.13.19",
            "v0.13.18",
            "v0.13.17",
            "v0.13.16",
            "v0.13.15",
            "v0.13.14",
            "v0.13.13",
            "v0.13.12",
            "v0.13.11",
            "v0.13.10",
            "v0.13.9",
            "v0.13.8",
            "v0.13.7",
            "v0.13.6",
            "v0.13.5",
            "v0.13.4",
            "v0.13.3",
            "v0.13.2",
            "v0.13.0",
            "v0.12.6",
            "v0.12.5",
            "v0.12.4",
            "v0.12.3",
            "v0.12.2",
            "v0.12.1",
            "v0.12.0",
            "v0.11.11",
            "v0.11.10",
            "v0.11.9",
            "v0.11.8",
            "v0.11.7",
            "v0.11.6",
            "v0.11.4",
            "v0.11.3",
            "v0.11.2",
            "v0.11.1",
            "v0.10.10",
            "v0.10.10-rc.1",
            "v0.10.10-rc.0",
            "v0.10.9",
            "v0.10.8",
            "v0.10.7",
            "v0.10.6",
            "v0.10.5",
            "v0.10.4",
            "v0.10.3",
            "v0.10.2",
            "v0.10.1",
            "v0.10.0",
            "v0.9.8",
            "v0.9.7",
            "v0.9.6",
            "v0.9.5",
            "v0.9.4",
            "v0.9.2",
            "v0.9.1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-75757.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:29.196026837Z",
      "provider": "osv",
      "references": [
        "https://cna.erlef.org/cves/CVE-2026-75757.html",
        "https://github.com",
        "https://osv.dev/vulnerability/EEF-CVE-2026-75757",
        "https://repo.hex.pm",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/75xxx/CVE-2026-75757.json",
        "https://github.com/ash-project/ash_admin/security/advisories/GHSA-3259-55fp-w94j",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-75757",
        "https://github.com/ash-project/ash_admin/commit/e93a3408a85035e1f90275d02bc2470c96095e56",
        "https://github.com/ash-project/ash_admin"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-565"
        ],
        "cna_assigner": "EEF",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/75xxx/CVE-2026-75757.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-75757",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 495766,
  "published_at": "2026-08-31T02:20:17.985+00:00"
}