ubuntu-cve-2026-27456
Vulnerability from osv_ubuntu
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.
{
"affected": [
{
"ecosystem_specific": {
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},
{
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},
{
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},
{
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},
{
"binary_name": "mount",
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},
{
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},
{
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},
{
"binary_name": "uuid-runtime",
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}
]
},
"package": {
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},
"ranges": [
{
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{
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}
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"2.20.1-5.1ubuntu13",
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"2.20.1-5.1ubuntu15",
"2.20.1-5.1ubuntu16",
"2.20.1-5.1ubuntu17",
"2.20.1-5.1ubuntu18",
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"2.20.1-5.1ubuntu20.1",
"2.20.1-5.1ubuntu20.2",
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{
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{
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{
"binary_name": "uuid-runtime",
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{
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{
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{
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{
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},
{
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]
},
"package": {
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"2.34-0.1ubuntu9",
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},
{
"ecosystem_specific": {
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{
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{
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"package": {
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{
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"package": {
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"name": "util-linux",
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"2.41.3-3ubuntu1",
"2.41.3-3ubuntu2"
]
}
],
"aliases": [],
"details": "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.",
"id": "UBUNTU-CVE-2026-27456",
"modified": "2026-05-20T15:26:07Z",
"published": "2026-04-03T22:16:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-27456"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-27456"
},
{
"type": "REPORT",
"url": "https://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9g"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-27456"
]
}
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.