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LinuxCVE-2024-43882

HistoryAug 21, 2024 - 1:15 a.m.

CVE-2024-43882

2024-08-2101:15:12

CWE-367

Linux

web.nvd.nist.gov

linux kernel

vulnerability

permission checking

file execution

toctou

setuid

setgid

race condition

package managers

chmod

inode_permission

CVSS3

Attack Vector

LOCAL

Attack Complexity

HIGH

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

AI Score

Confidence

High

EPSS

Percentile

5.1%

JSON

In the Linux kernel, the following vulnerability has been resolved:

exec: Fix ToCToU between perm check and set-uid/gid usage

When opening a file for exec via do_filp_open(), permission checking is
done against the file’s metadata at that moment, and on success, a file
pointer is passed back. Much later in the execve() code path, the file
metadata (specifically mode, uid, and gid) is used to determine if/how
to set the uid and gid. However, those values may have changed since the
permissions check, meaning the execution may gain unintended privileges.

For example, if a file could change permissions from executable and not
set-id:

---------x 1 root root 16048 Aug 7 13:16 target

to set-id and non-executable:

—S------ 1 root root 16048 Aug 7 13:16 target

it is possible to gain root privileges when execution should have been
disallowed.

While this race condition is rare in real-world scenarios, it has been
observed (and proven exploitable) when package managers are updating
the setuid bits of installed programs. Such files start with being
world-executable but then are adjusted to be group-exec with a set-uid
bit. For example, “chmod o-x,u+s target” makes “target” executable only
by uid “root” and gid “cdrom”, while also becoming setuid-root:

-rwxr-xr-x 1 root cdrom 16048 Aug 7 13:16 target

becomes:

-rwsr-xr-- 1 root cdrom 16048 Aug 7 13:16 target

But racing the chmod means users without group “cdrom” membership can
get the permission to execute “target” just before the chmod, and when
the chmod finishes, the exec reaches brpm_fill_uid(), and performs the
setuid to root, violating the expressed authorization of “only cdrom
group members can setuid to root”.

Re-check that we still have execute permissions in case the metadata
has changed. It would be better to keep a copy from the perm-check time,
but until we can do that refactoring, the least-bad option is to do a
full inode_permission() call (under inode lock). It is understood that
this is safe against dead-locks, but hardly optimal.

Affected configurations

Nvd

Vulners

Node

linuxlinux_kernelRange<4.19.320

linuxlinux_kernelRange4.20–5.4.282

linuxlinux_kernelRange5.5–5.10.224

linuxlinux_kernelRange5.11–5.15.165

linuxlinux_kernelRange5.16–6.1.106

linuxlinux_kernelRange6.2–6.6.47

linuxlinux_kernelRange6.7–6.10.6

linuxlinux_kernelMatch6.11rc1

linuxlinux_kernelMatch6.11rc2

linuxlinux_kernelMatch6.11rc3

VendorProductVersionCPE
linuxlinux_kernel*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linuxlinux_kernel6.11cpe:2.3:o:linux:linux_kernel:6.11:rc1:*:*:*:*:*:*
linuxlinux_kernel6.11cpe:2.3:o:linux:linux_kernel:6.11:rc2:*:*:*:*:*:*
linuxlinux_kernel6.11cpe:2.3:o:linux:linux_kernel:6.11:rc3:*:*:*:*:*:*

Vendor	Product	Version	CPE
linux	linux_kernel	*	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	6.11	cpe:2.3:o:linux:linux_kernel:6.11:rc1::::::
linux	linux_kernel	6.11	cpe:2.3:o:linux:linux_kernel:6.11:rc2::::::
linux	linux_kernel	6.11	cpe:2.3:o:linux:linux_kernel:6.11:rc3::::::

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "fs/exec.c"
    ],
    "versions": [
      {
        "version": "1da177e4c3f4",
        "lessThan": "d5c3c7e26275",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "368f6985d466",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "15469d46ba34",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "9b424c5d4130",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "f6cfc6bcfd5e",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "d2a2a4714d80",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "90dfbba89ad4",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "f50733b45d86",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "fs/exec.c"
    ],
    "versions": [
      {
        "version": "4.19.320",
        "lessThanOrEqual": "4.19.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.4.282",
        "lessThanOrEqual": "5.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.10.224",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.15.165",
        "lessThanOrEqual": "5.15.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.1.106",
        "lessThanOrEqual": "6.1.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.6.47",
        "lessThanOrEqual": "6.6.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.10.6",
        "lessThanOrEqual": "6.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.11",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]