CVE-2026-13048
Data::MuForm::Localizer versions through 0.05 for Perl execute Perl from a message catalog header, reached at an arbitrary path because load_lexicon interpolates the language attribute into the catalog filename.
load_lexicon builds the catalog path by appending `Messages/$lang.po` to the directory holding Localizer.pm, where $lang is the language attribute, with no check that it names a bare locale tag. A value holding `../` segments walks out of the message directory, so any readable path with a `.po` suffix is loaded.
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While parsing the catalog, extract_header_msgstr takes the `Plural-Forms:` header, prefixes `$` to the bare words nplurals, plural and n, and passes the rest verbatim into a string that is evaluated: the nplurals form evaluates the header expression immediately, and the plural_code form compiles it into a subroutine whose body runs when a plural message is localized. A header of `nplurals=2; plural=(system('...'),0);` therefore runs that command as the catalog loads. The evaluation inherits strict, so an expression that assigns to an undeclared variable fails to compile, while one built from calls alone does not.
An application that sets the language attribute from request data, an Accept-Language header or a locale parameter, and an attacker who can place a file with a `.po` suffix and chosen contents at a readable path, together give code execution as the application user. The message expansion path is not affected: expand_named substitutes only the placeholder names the caller supplies, and _mangle_value returns the value unchanged.
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
- Puntuación base: 8.2
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.56%
- Percentil entre todas las CVEs puntuadas: 45
- Fecha de la puntuación: 6/10/2026
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).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1190Exploit Public-Facing Applicationinitial access85 % - Impacto principal
T1059Command and Scripting Interpreterexecution90 % - Impacto secundario
T1005Data from Local Systemcollection75 %
Aplicación expuesta en red sin autenticación (AV:N/PR:N) que interpola entrada no validada en ruta de archivo, permitiendo ejecución de código Perl arbitrario mediante inyección en cabecera de catálogo .po. CWE-22 + CWE-95 confirman path traversal y evaluación dinámica.
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
CWE
- CWE-22, CWE-95
Referencias
- https://metacpan.org/release/GSHANK/Data-MuForm-0.05/source/lib/Data/MuForm/Localizer.pm#L381-428
- https://metacpan.org/release/GSHANK/Data-MuForm-0.05/source/lib/Data/MuForm/Localizer.pm#L56-63
- https://security.metacpan.org/patches/D/Data-MuForm/0.05/CVE-2026-13048-r2.patch
- http://www.openwall.com/lists/oss-security/2026/08/13/10
JSON original (NVD)
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{
"id": "CVE-2026-13048",
"cveTags": [],
"metrics": {
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-13048",
"role": "CISA Coordinator",
"options": [
{
"exploitation": "none"
},
{
"automatable": "yes"
},
{
"technicalImpact": "partial"
}
],
"version": "2.0.3",
"timestamp": "2026-08-14T11:31:37.959480Z"
}
}
],
"cvssMetricV31": [
{
"type": "Secondary",
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 8.2,
"attackVector": "NETWORK",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "NONE",
"privilegesRequired": "NONE",
"confidentialityImpact": "LOW"
},
"impactScore": 4.2,
"exploitabilityScore": 3.9
}
]
},
"affected": [
{
"source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
"affectedData": [
{
"repo": "https://github.com/gshank/data-muform",
"modules": [
"Data::MuForm::Localizer"
],
"versions": [
{
"status": "affected",
"version": "0",
"versionType": "custom",
"lessThanOrEqual": "0.05"
}
],
"packageURL": "pkg:cpan/Data-MuForm",
"packageName": "Data-MuForm",
"programFiles": [
"lib/Data/MuForm/Localizer.pm"
],
"collectionURL": "https://cpan.org/modules",
"defaultStatus": "unaffected",
"programRoutines": [
{
"name": "Data::MuForm::Localizer::load_lexicon"
},
{
"name": "Data::MuForm::Localizer::extract_header_msgstr"
},
{
"name": "Data::MuForm::Localizer::get_lexicon"
}
]
}
]
}
],
"published": "2026-08-13T17:17:19.397",
"references": [
{
"url": "https://metacpan.org/release/GSHANK/Data-MuForm-0.05/source/lib/Data/MuForm/Localizer.pm#L381-428",
"source": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
},
{
"url": "https://metacpan.org/release/GSHANK/Data-MuForm-0.05/source/lib/Data/MuForm/Localizer.pm#L56-63",
"source": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
},
{
"url": "https://security.metacpan.org/patches/D/Data-MuForm/0.05/CVE-2026-13048-r2.patch",
"source": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
},
{
"url": "http://www.openwall.com/lists/oss-security/2026/08/13/10",
"source": "af854a3a-2127-422b-91ae-364da2661108"
}
],
"vulnStatus": "Deferred",
"weaknesses": [
{
"type": "Secondary",
"source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
"description": [
{
"lang": "en",
"value": "CWE-22"
},
{
"lang": "en",
"value": "CWE-95"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "Data::MuForm::Localizer versions through 0.05 for Perl execute Perl from a message catalog header, reached at an arbitrary path because load_lexicon interpolates the language attribute into the catalog filename.\n\nload_lexicon builds the catalog path by appending `Messages/$lang.po` to the directory holding Localizer.pm, where $lang is the language attribute, with no check that it names a bare locale tag. A value holding `../` segments walks out of the message directory, so any readable path with a `.po` suffix is loaded. While parsing the catalog, extract_header_msgstr takes the `Plural-Forms:` header, prefixes `$` to the bare words nplurals, plural and n, and passes the rest verbatim into a string that is evaluated: the nplurals form evaluates the header expression immediately, and the plural_code form compiles it into a subroutine whose body runs when a plural message is localized. A header of `nplurals=2; plural=(system('...'),0);` therefore runs that command as the catalog loads. The evaluation inherits strict, so an expression that assigns to an undeclared variable fails to compile, while one built from calls alone does not.\n\nAn application that sets the language attribute from request data, an Accept-Language header or a locale parameter, and an attacker who can place a file with a `.po` suffix and chosen contents at a readable path, together give code execution as the application user. The message expansion path is not affected: expand_named substitutes only the placeholder names the caller supplies, and _mangle_value returns the value unchanged."
}
],
"lastModified": "2026-08-26T16:51:19.490",
"sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
}