CVE-2026-27456 (GCVE-0-2026-27456)
Vulnerability from cvelistv5 – Published: 2026-04-03 21:23 – Updated: 2026-04-06 15:42
VLAI
EPSS
VEX
Title
util-linux: TOCTOU Race Condition in util-linux mount(8) - Loop Device Setup
Summary
util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a TOCTOU (Time-of-Check-Time-of-Use) vulnerability has been identified in the SUID binary /usr/bin/mount from util-linux. The mount binary, when setting up loop devices, validates the source file path with user privileges via fork() + setuid() + realpath(), but subsequently re-canonicalizes and opens it with root privileges (euid=0) without verifying that the path has not been replaced between both operations. Neither O_NOFOLLOW, nor inode comparison, nor post-open fstat() are employed. This allows a local unprivileged user to replace the source file with a symlink pointing to any root-owned file or device during the race window, causing the SUID binary to open and mount it as root. Exploitation requires an /etc/fstab entry with user,loop options whose path points to a directory where the attacker has write permission, and that /usr/bin/mount has the SUID bit set (the default configuration on virtually all Linux distributions). The impact is unauthorized read access to root-protected files and block devices, including backup images, disk volumes, and any file containing a valid filesystem. This issue has been patched in version 2.41.4.
Severity
4.7 (Medium)
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-04-06 15:38 UTC
CWE
Assigner
References
3 references
| URL | Tags |
|---|---|
| https://github.com/util-linux/util-linux/security… | x_refsource_CONFIRM |
| https://github.com/util-linux/util-linux/commit/5… | x_refsource_MISC |
| https://github.com/util-linux/util-linux/releases… | x_refsource_MISC |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| util-linux | util-linux |
Affected:
< 2.41.4
|
guessed |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-27456",
"options": [
{
"Exploitation": "poc"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-04-06T15:38:42.794607Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-04-06T15:42:35.774Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"exploit"
],
"url": "https://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9g"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "util-linux",
"vendor": "util-linux",
"versions": [
{
"status": "affected",
"version": "\u003c 2.41.4"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a TOCTOU (Time-of-Check-Time-of-Use) vulnerability has been identified in the SUID binary /usr/bin/mount from util-linux. The mount binary, when setting up loop devices, validates the source file path with user privileges via fork() + setuid() + realpath(), but subsequently re-canonicalizes and opens it with root privileges (euid=0) without verifying that the path has not been replaced between both operations. Neither O_NOFOLLOW, nor inode comparison, nor post-open fstat() are employed. This allows a local unprivileged user to replace the source file with a symlink pointing to any root-owned file or device during the race window, causing the SUID binary to open and mount it as root. Exploitation requires an /etc/fstab entry with user,loop options whose path points to a directory where the attacker has write permission, and that /usr/bin/mount has the SUID bit set (the default configuration on virtually all Linux distributions). The impact is unauthorized read access to root-protected files and block devices, including backup images, disk volumes, and any file containing a valid filesystem. This issue has been patched in version 2.41.4."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "HIGH",
"attackVector": "LOCAL",
"availabilityImpact": "NONE",
"baseScore": 4.7,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "HIGH",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-59",
"description": "CWE-59: Improper Link Resolution Before File Access (\u0027Link Following\u0027)",
"lang": "en",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"cweId": "CWE-269",
"description": "CWE-269: Improper Privilege Management",
"lang": "en",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"cweId": "CWE-367",
"description": "CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-04-03T21:23:00.984Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9g",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9g"
},
{
"name": "https://github.com/util-linux/util-linux/commit/5e390467b26a3cf3fecc04e1a0d482dff3162fc4",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/util-linux/util-linux/commit/5e390467b26a3cf3fecc04e1a0d482dff3162fc4"
},
{
"name": "https://github.com/util-linux/util-linux/releases/tag/v2.41.4",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/util-linux/util-linux/releases/tag/v2.41.4"
}
],
"source": {
"advisory": "GHSA-qq4x-vfq4-9h9g",
"discovery": "UNKNOWN"
},
"title": "util-linux: TOCTOU Race Condition in util-linux mount(8) - Loop Device Setup"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-27456",
"datePublished": "2026-04-03T21:23:00.984Z",
"dateReserved": "2026-02-19T17:25:31.100Z",
"dateUpdated": "2026-04-06T15:42:35.774Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-27456",
"date": "2026-10-06",
"epss": "0.00118",
"percentile": "0.01559"
},
"microsoft_vex": {
"current_release_date": "2026-09-25T02:31:01.000Z",
"cve": "CVE-2026-27456",
"id": "msrc_CVE-2026-27456",
"initial_release_date": "2026-04-05T01:02:24.000Z",
"product_status:fixed": "4",
"product_status:known_affected": "4",
"source": "Microsoft CSAF VEX",
"status": "final",
"title": "util-linux: TOCTOU Race Condition in util-linux mount(8) - Loop Device Setup",
"url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-27456.json",
"version": "8"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"product": "util-linux",
"vendor": "util-linux",
"versions": [
{
"status": "affected",
"version": "\u003c 2.41.4"
}
]
}
],
"source": "security-advisories@github.com"
}
],
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:kernel:util-linux:*:*:*:*:*:*:*:*",
"matchCriteriaId": "A0F464C1-2AC1-4B59-B522-89DD9D072C7F",
"versionEndExcluding": "2.41.4",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a TOCTOU (Time-of-Check-Time-of-Use) vulnerability has been identified in the SUID binary /usr/bin/mount from util-linux. The mount binary, when setting up loop devices, validates the source file path with user privileges via fork() + setuid() + realpath(), but subsequently re-canonicalizes and opens it with root privileges (euid=0) without verifying that the path has not been replaced between both operations. Neither O_NOFOLLOW, nor inode comparison, nor post-open fstat() are employed. This allows a local unprivileged user to replace the source file with a symlink pointing to any root-owned file or device during the race window, causing the SUID binary to open and mount it as root. Exploitation requires an /etc/fstab entry with user,loop options whose path points to a directory where the attacker has write permission, and that /usr/bin/mount has the SUID bit set (the default configuration on virtually all Linux distributions). The impact is unauthorized read access to root-protected files and block devices, including backup images, disk volumes, and any file containing a valid filesystem. This issue has been patched in version 2.41.4."
},
{
"lang": "es",
"value": "util-linux es una colecci\u00f3n aleatoria de utilidades de Linux. Antes de la versi\u00f3n 2.41.4, se ha identificado una vulnerabilidad TOCTOU (Time-of-Check-Time-of-Use) en el binario SUID /usr/bin/mount de util-linux. El binario mount, al configurar dispositivos de bucle, valida la ruta del archivo de origen con privilegios de usuario a trav\u00e9s de fork() + setuid() + realpath(), pero posteriormente la vuelve a canonizar y la abre con privilegios de root (euid=0) sin verificar que la ruta no haya sido reemplazada entre ambas operaciones. No se emplean ni O_NOFOLLOW, ni la comparaci\u00f3n de inodos, ni fstat() posterior a la apertura. Esto permite a un usuario local sin privilegios reemplazar el archivo de origen con un enlace simb\u00f3lico que apunte a cualquier archivo o dispositivo propiedad de root durante la ventana de carrera, haciendo que el binario SUID lo abra y monte como root. La explotaci\u00f3n requiere una entrada en /etc/fstab con las opciones user,loop cuya ruta apunte a un directorio donde el atacante tenga permiso de escritura, y que /usr/bin/mount tenga el bit SUID establecido (la configuraci\u00f3n predeterminada en pr\u00e1cticamente todas las distribuciones de Linux). El impacto es el acceso de lectura no autorizado a archivos protegidos por root y dispositivos de bloque, incluyendo im\u00e1genes de respaldo, vol\u00famenes de disco y cualquier archivo que contenga un sistema de archivos v\u00e1lido. Este problema ha sido parcheado en la versi\u00f3n 2.41.4."
}
],
"id": "CVE-2026-27456",
"lastModified": "2026-07-24T22:10:00.140",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "HIGH",
"attackVector": "LOCAL",
"availabilityImpact": "NONE",
"baseScore": 4.7,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "HIGH",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N",
"version": "3.1"
},
"exploitabilityScore": 1.0,
"impactScore": 3.6,
"source": "security-advisories@github.com",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-27456",
"options": [
{
"exploitation": "poc"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-04-06T15:38:42.794607Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-04-03T22:16:25.400",
"references": [
{
"source": "security-advisories@github.com",
"tags": [
"Patch"
],
"url": "https://github.com/util-linux/util-linux/commit/5e390467b26a3cf3fecc04e1a0d482dff3162fc4"
},
{
"source": "security-advisories@github.com",
"tags": [
"Product"
],
"url": "https://github.com/util-linux/util-linux/releases/tag/v2.41.4"
},
{
"source": "security-advisories@github.com",
"tags": [
"Exploit",
"Vendor Advisory"
],
"url": "https://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9g"
},
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"tags": [
"Exploit",
"Vendor Advisory"
],
"url": "https://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9g"
}
],
"sourceIdentifier": "security-advisories@github.com",
"vulnStatus": "Analyzed",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-59"
},
{
"lang": "en",
"value": "CWE-269"
},
{
"lang": "en",
"value": "CWE-367"
}
],
"source": "security-advisories@github.com",
"type": "Secondary"
},
{
"description": [
{
"lang": "en",
"value": "CWE-367"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
}
},
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-09-16T02:28:16+00:00",
"cve": "CVE-2026-27456",
"id": "CVE-2026-27456",
"initial_release_date": "2026-04-03T21:23:00.984000+00:00",
"product_status:fixed": "3",
"product_status:known_affected": "47",
"product_status:known_not_affected": "16",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "util-linux: TOCTOU in the mount program when setting up loop devices",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27456.json",
"version": "3"
},
"suse_vex": {
"aggregate_severity": "moderate",
"current_release_date": "2026-09-29T23:59:01Z",
"cve": "CVE-2026-27456",
"id": "CVE-2026-27456",
"initial_release_date": "2026-04-07T23:27:43Z",
"product_status:known_affected": "584",
"product_status:recommended": "604",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-27456",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-27456.json",
"version": "29"
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-27456",
"options": [
{
"Exploitation": "poc"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-04-06T15:38:42.794607Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-04-06T15:38:52.451Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"exploit"
],
"url": "https://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9g"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "util-linux",
"vendor": "util-linux",
"versions": [
{
"status": "affected",
"version": "\u003c 2.41.4"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a TOCTOU (Time-of-Check-Time-of-Use) vulnerability has been identified in the SUID binary /usr/bin/mount from util-linux. The mount binary, when setting up loop devices, validates the source file path with user privileges via fork() + setuid() + realpath(), but subsequently re-canonicalizes and opens it with root privileges (euid=0) without verifying that the path has not been replaced between both operations. Neither O_NOFOLLOW, nor inode comparison, nor post-open fstat() are employed. This allows a local unprivileged user to replace the source file with a symlink pointing to any root-owned file or device during the race window, causing the SUID binary to open and mount it as root. Exploitation requires an /etc/fstab entry with user,loop options whose path points to a directory where the attacker has write permission, and that /usr/bin/mount has the SUID bit set (the default configuration on virtually all Linux distributions). The impact is unauthorized read access to root-protected files and block devices, including backup images, disk volumes, and any file containing a valid filesystem. This issue has been patched in version 2.41.4."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "HIGH",
"attackVector": "LOCAL",
"availabilityImpact": "NONE",
"baseScore": 4.7,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "HIGH",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-59",
"description": "CWE-59: Improper Link Resolution Before File Access (\u0027Link Following\u0027)",
"lang": "en",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"cweId": "CWE-269",
"description": "CWE-269: Improper Privilege Management",
"lang": "en",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"cweId": "CWE-367",
"description": "CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-04-03T21:23:00.984Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9g",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9g"
},
{
"name": "https://github.com/util-linux/util-linux/commit/5e390467b26a3cf3fecc04e1a0d482dff3162fc4",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/util-linux/util-linux/commit/5e390467b26a3cf3fecc04e1a0d482dff3162fc4"
},
{
"name": "https://github.com/util-linux/util-linux/releases/tag/v2.41.4",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/util-linux/util-linux/releases/tag/v2.41.4"
}
],
"source": {
"advisory": "GHSA-qq4x-vfq4-9h9g",
"discovery": "UNKNOWN"
},
"title": "util-linux: TOCTOU Race Condition in util-linux mount(8) - Loop Device Setup"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-27456",
"datePublished": "2026-04-03T21:23:00.984Z",
"dateReserved": "2026-02-19T17:25:31.100Z",
"dateUpdated": "2026-04-06T15:42:35.774Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- 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.
Loading…
Loading…
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.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
Loading…