Vulnerability-Lookup

CVE-2026-49401 (GCVE-0-2026-49401)

Vulnerability from cvelistv5 – Published: 2026-06-23 17:22 – Updated: 2026-07-31 13:15

Title

Deno Permission Bypass via Unicode Normalization Mismatch on macOS (APFS)

Summary

Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.7.14, Deno's permission system enforces filesystem and execution restrictions by comparing the requested path against the path supplied to --deny-read, --deny-write, --deny-run, or --deny-ffi. On macOS, that comparison was done at the raw-byte level while the APFS filesystem treats different Unicode spellings of the same name as the same file. That means a program could reach a denied path by spelling it differently than the deny rule. This vulnerability is fixed in 2.7.14.

Severity

7.3 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-23 17:35 UTC

CWE

CWE-41 - Improper Resolution of Path Equivalence
CWE-176 - Improper Handling of Unicode Encoding

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 8026 records in the last 180 days details

References

1 reference

URL	Tags
https://github.com/denoland/deno/security/advisor…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version	CPE status
denoland	deno	Affected: < 2.7.14	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-49401

Vulnerability from fkie_nvd - Published: 2026-06-23 18:18 - Updated: 2026-10-25 23:10

Severity

7.3 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:N
8.4 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/denoland/deno/security/advisories/GHSA-8xpq-cjcf-3wh9	Exploit, Mitigation, Vendor Advisory

Impacted products

	Vendor	Product	Version
	deno	deno	*
	apple	macos	-

JSON

To clipboard

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GHSA-8XPQ-CJCF-3WH9

Vulnerability from github – Published: 2026-06-16 19:11 – Updated: 2026-07-31 13:15

Summary

Deno: Permission Bypass via Unicode Normalization Mismatch on macOS (APFS)

Details

Summary

Deno's permission system enforces filesystem and execution restrictions by comparing the requested path against the path supplied to --deny-read, --deny-write, --deny-run, or --deny-ffi. On macOS, that comparison was done at the raw-byte level while the APFS filesystem treats different Unicode spellings of the same name as the same file.

That means a program could reach a denied path by spelling it differently than the deny rule. For example, with --deny-read=/secrets/passwörter.txt, a script could still read the file by opening /secrets/passwo\u0308rter.txt (NFD instead of NFC), or /SECRETS/PASSWÖRTER.txt (different case, since default APFS volumes are case-insensitive). Other forms include ligature characters (ﬁ vs fi, ﬀ vs ff, …) and German ß vs ss.

The denied path and the requested path differed at the byte level, so Deno's permission check passed; the kernel then resolved them to the same inode and served the file anyway. The same flaw affected --deny-write, --deny-run, and --deny-ffi, which share the same path-comparison code.

Am I affected?

You are potentially affected if all of the following are true:

You run Deno on macOS (the issue is specific to APFS path-equivalence rules; Linux and Windows are not affected by this variant).
You rely on --deny-read, --deny-write, --deny-run, or --deny-ffi as a security boundary against less-trusted code — a dependency, plugin, or attacker-controlled input.
The protected path contains characters that have alternate Unicode spellings — most commonly accented characters (é, ñ, ö, …), German ß, or Latin ligatures — or you rely on case-sensitivity on a default APFS volume.

If you only run fully trusted code, or your deny rules cover paths that are pure ASCII with no case-sensitive aliases, you are not exposed to this specific bypass.

Impact

A program running with broad --allow-read (or --allow-write / --allow-run / --allow-ffi) but with --deny-* carve-outs for specific paths could read, write, execute, or load via FFI those denied paths by referring to them through a Unicode- or case-equivalent spelling. The sandbox model on macOS was weaker than the flags suggested.

Workaround

If you cannot upgrade immediately:

Prefer --allow-* allowlists over --deny-* denylists. Allow rules match against the original specifier, so an attacker-supplied alternate spelling will not match a path you didn't explicitly grant.
Do not rely on case-sensitivity of paths on macOS for security boundaries; default APFS volumes are case-insensitive.

Fix

On macOS, Deno now normalizes both the deny-rule path and the requested path to NFC and applies Unicode case folding before comparing them. This matches how APFS resolves paths at the inode level, so byte-different but equivalent spellings are now rejected by the same deny rule.

Severity

7.3 (High)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:N

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.7.13"
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "deno"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.7.14"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-49401"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-176",
      "CWE-41"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-16T19:11:52Z",
    "nvd_published_at": "2026-06-23T18:18:03Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nDeno\u0027s permission system enforces filesystem and execution restrictions by\ncomparing the requested path against the path supplied to `--deny-read`,\n`--deny-write`, `--deny-run`, or `--deny-ffi`. On macOS, that comparison was\ndone at the raw-byte level while the APFS filesystem treats different Unicode\nspellings of the same name as the same file.\n\nThat means a program could reach a denied path by spelling it differently than\nthe deny rule. For example, with `--deny-read=/secrets/passw\u00f6rter.txt`, a\nscript could still read the file by opening `/secrets/passwo\\u0308rter.txt`\n(NFD instead of NFC), or `/SECRETS/PASSW\u00d6RTER.txt` (different case, since\ndefault APFS volumes are case-insensitive). Other forms include ligature\ncharacters (`\ufb01` vs `fi`, `\ufb00` vs `ff`, \u2026) and German `\u00df` vs `ss`.\n\nThe denied path and the requested path differed at the byte level, so Deno\u0027s\npermission check passed; the kernel then resolved them to the same inode and\nserved the file anyway. The same flaw affected `--deny-write`, `--deny-run`,\nand `--deny-ffi`, which share the same path-comparison code.\n\n## Am I affected?\n\nYou are potentially affected if **all** of the following are true:\n\n1. You run Deno on **macOS** (the issue is specific to APFS path-equivalence\n   rules; Linux and Windows are not affected by this variant).\n2. You rely on `--deny-read`, `--deny-write`, `--deny-run`, or `--deny-ffi`\n   as a security boundary against less-trusted code \u2014 a dependency, plugin,\n   or attacker-controlled input.\n3. The protected path contains characters that have alternate Unicode\n   spellings \u2014 most commonly accented characters (`\u00e9`, `\u00f1`, `\u00f6`, \u2026), German\n   `\u00df`, or Latin ligatures \u2014 or you rely on case-sensitivity on a default\n   APFS volume.\n\nIf you only run fully trusted code, or your deny rules cover paths that are\npure ASCII with no case-sensitive aliases, you are not exposed to this\nspecific bypass.\n\n## Impact\n\nA program running with broad `--allow-read` (or `--allow-write` /\n`--allow-run` / `--allow-ffi`) but with `--deny-*` carve-outs for specific\npaths could read, write, execute, or load via FFI those denied paths by\nreferring to them through a Unicode- or case-equivalent spelling. The sandbox\nmodel on macOS was weaker than the flags suggested.\n\n## Workaround\n\nIf you cannot upgrade immediately:\n\n- Prefer `--allow-*` allowlists over `--deny-*` denylists. Allow rules match\n   against the original specifier, so an attacker-supplied alternate spelling\n   will not match a path you didn\u0027t explicitly grant.\n- Do not rely on case-sensitivity of paths on macOS for security boundaries;\n   default APFS volumes are case-insensitive.\n\n## Fix\n\nOn macOS, Deno now normalizes both the deny-rule path and the requested path\nto NFC and applies Unicode case folding before comparing them. This matches\nhow APFS resolves paths at the inode level, so byte-different but equivalent\nspellings are now rejected by the same deny rule.",
  "id": "GHSA-8xpq-cjcf-3wh9",
  "modified": "2026-07-31T13:15:54Z",
  "published": "2026-06-16T19:11:52Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/denoland/deno/security/advisories/GHSA-8xpq-cjcf-3wh9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-49401"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/denoland/deno"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Deno: Permission Bypass via Unicode Normalization Mismatch on macOS (APFS)"
}

Sightings

Author	Source	Type	Date	Other

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Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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CVE-2026-49401 (GCVE-0-2026-49401)

FKIE_CVE-2026-49401

GHSA-8XPQ-CJCF-3WH9

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