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YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack

Type: advisorySources: OSV

YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack. In the bundled libsyck, when an anchor name is redefined or removed, syck_hdlr_add_anchor and syck_hdlr_remove_anchor free the node stored under that name with syck_free_node. That node can still be live on the parser's value stack, so syck_hdlr_add_node reaches it again and frees it a second time. On a normal build the 48-byte node chunk is freed twice and the interpreter aborts. Anchors need no special flags, so this is reached on the default Load path, and a 7-byte document that redefines an anchor triggers it. Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor mid-parse crashes the interpreter, a denial of service.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-13713
Confirmed fixed CVEs
Not specified
Updated in this feed
4 Nov 2026, 13:13 UTC · Revision 1

Source evidence

YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack

core-osv · Original source

Published 16 Jul 2026, 21:35 UTC

YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack. In the bundled libsyck, when an anchor name is redefined or removed, syck_hdlr_add_anchor and syck_hdlr_remove_anchor free the node stored under that name with syck_free_node. That node can still be live on the parser's value stack, so syck_hdlr_add_node reaches it again and frees it a second time. On a normal build the 48-byte node chunk is freed twice and the interpreter aborts. Anchors need no special flags, so this is reached on the default Load path, and a 7-byte document that redefines an anchor triggers it. Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor mid-parse crashes the interpreter, a denial of service.

osv:CVE-2026-13713
Complete source record
{
  "id": "5be32a757613c4b9d235425b4f4274b6d14ec0c106e13338af6f92da6742d788",
  "url": "https://osv.dev/vulnerability/CVE-2026-13713",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack",
    "summary": "YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack. In the bundled libsyck, when an anchor name is redefined or removed, syck_hdlr_add_anchor and syck_hdlr_remove_anchor free the node stored under that name with syck_free_node. That node can still be live on the parser's value stack, so syck_hdlr_add_node reaches it again and frees it a second time. On a normal build the 48-byte node chunk is freed twice and the interpreter aborts. Anchors need no special flags, so this is reached on the default Load path, and a 7-byte document that redefines an anchor triggers it. Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor mid-parse crashes the interpreter, a denial of service.",
    "evidence": "osv:CVE-2026-13713",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-13713",
      "aliases": [
        "CVE-2026-13713"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/cpan-authors/YAML-Syck",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "d7f942870d2f57b17dd5db1b3714eff448c34cd6"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.47"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "fixed": "44c90a109ec3215ee7ce747bd11209835e123d8b"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
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            "1.44",
            "1.43",
            "1.42",
            "1.41",
            "1.39",
            "1.38",
            "1.37",
            "1.37_01",
            "1.36",
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            "1.33",
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            "1.21_01",
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            "1.11",
            "1.10_07",
            "1.10_06",
            "1.10_05",
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            "1.10_02",
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            "0.72",
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            "0.70",
            "0.67",
            "0.66",
            "0.65",
            "0.64",
            "0.63",
            "0.62",
            "0.61",
            "0.60",
            "0.46_01",
            "0.45",
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            "0.06",
            "0.05",
            "0.04",
            "0.03",
            "0.02",
            "0.01"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-13713.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:35.345224833Z",
      "provider": "osv",
      "references": [
        "https://cpan.org/modules",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/13xxx/CVE-2026-13713.json",
        "https://metacpan.org/release/TODDR/YAML-Syck-1.47/changes",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-13713",
        "https://github.com/toddr/YAML-Syck/commit/44c90a109ec3215ee7ce747bd11209835e123d8b.patch",
        "https://github.com/toddr/YAML-Syck"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-415",
          "CWE-416"
        ],
        "cna_assigner": "CPANSec",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/13xxx/CVE-2026-13713.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-13713",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 502930,
  "published_at": "2026-07-16T21:35:31.477+00:00"
}