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CVE-2026-19487

Estado: Pendiente de análisisMedia (5.3)—

Perl versions from 5.9.4 before 5.41.9 produce incorrect regular expression match results when a stale failure flag ends the Aho-Corasick prescan early in S_find_byclass.

The prescan walks the subject for positions where the full pattern could match, and the engine tries it from the leftmost one recorded. A failing transition sets the failed flag, and a later successful transition does not clear it, so the prescan reads the stale flag as a failure and stops before it can record a candidate that starts earlier. It takes a subject where one candidate is recorded and a later character then forces a fallback through a fail link that succeeds.

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Example:

An alternation like this can miss input it should match, or match it on the wrong branch, so an access or filtering decision made from the result can be wrong.

Detalles técnicos trazas, registros y código del informe original
  "ABCDE" =~ m/ABCF|BCDE|C/;    # matches C at offset 2, not BCDE
  "ABCDE" =~ m/ABCF|BCDE|C(G)/; # no match, BCDE missed

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Perl — PerlAI

CWE

Referencias

JSON original (NVD)

Mostrar
{
  "id": "CVE-2026-19487",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-19487",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-08-13T17:47:48.584748Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.3,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "LOW",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 1.4,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "affectedData": [
        {
          "repo": "https://github.com/Perl/perl5",
          "modules": [
            "perl"
          ],
          "versions": [
            {
              "status": "affected",
              "version": "5.9.4",
              "lessThan": "5.41.9",
              "versionType": "custom"
            }
          ],
          "packageURL": "pkg:cpan/perl",
          "packageName": "perl",
          "programFiles": [
            "regexec.c"
          ],
          "collectionURL": "https://cpan.org/modules",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "S_find_byclass"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-08-13T16:17:59.440",
  "references": [
    {
      "url": "https://github.com/Perl/perl5/commit/1a21abacaf6f684928bae8baaa153733c8c238eb.patch",
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
    },
    {
      "url": "https://github.com/Perl/perl5/issues/22892",
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
    },
    {
      "url": "http://www.openwall.com/lists/oss-security/2026/08/13/8",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://github.com/Perl/perl5/issues/22892",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
    }
  ],
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "description": [
        {
          "lang": "en",
          "value": "CWE-670"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Perl versions from 5.9.4 before 5.41.9 produce incorrect regular expression match results when a stale failure flag ends the Aho-Corasick prescan early in S_find_byclass.\n\nThe prescan walks the subject for positions where the full pattern could match, and the engine tries it from the leftmost one recorded. A failing transition sets the failed flag, and a later successful transition does not clear it, so the prescan reads the stale flag as a failure and stops before it can record a candidate that starts earlier. It takes a subject where one candidate is recorded and a later character then forces a fallback through a fail link that succeeds.\n\nExample:\n\n  \"ABCDE\" =~ m/ABCF|BCDE|C/;    # matches C at offset 2, not BCDE\n  \"ABCDE\" =~ m/ABCF|BCDE|C(G)/; # no match, BCDE missed\n\nAn alternation like this can miss input it should match, or match it on the wrong branch, so an access or filtering decision made from the result can be wrong."
    }
  ],
  "lastModified": "2026-08-28T15:42:20.060",
  "sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
}