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

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Summary

CVECVE-2024-43882
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2024-08-21 01:15:12 UTC
Updated2026-05-12 12:17:08 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 7 HIGH from [email protected]

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

Problem Types: CWE-367 | CWE-367 CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary7HIGHCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1ADPDECLARED8.4HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary8.4HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 9167b0b9a0ab7907191523f5a0528e3b9c288e21 d5c3c7e26275a2d83b894d30f7582a42853a958f git Not specified
CNA Linux Linux affected 9167b0b9a0ab7907191523f5a0528e3b9c288e21 368f6985d46657b8b466a421dddcacd4051f7ada git Not specified
CNA Linux Linux affected 9167b0b9a0ab7907191523f5a0528e3b9c288e21 15469d46ba34559bfe7e3de6659115778c624759 git Not specified
CNA Linux Linux affected 9167b0b9a0ab7907191523f5a0528e3b9c288e21 9b424c5d4130d56312e2a3be17efb0928fec4d64 git Not specified
CNA Linux Linux affected 9167b0b9a0ab7907191523f5a0528e3b9c288e21 f6cfc6bcfd5e1cf76115b6450516ea4c99897ae1 git Not specified
CNA Linux Linux affected 9167b0b9a0ab7907191523f5a0528e3b9c288e21 d2a2a4714d80d09b0f8eb6438ab4224690b7121e git Not specified
CNA Linux Linux affected 9167b0b9a0ab7907191523f5a0528e3b9c288e21 90dfbba89ad4f0d9c9744ecbb1adac4aa2ff4f3e git Not specified
CNA Linux Linux affected 9167b0b9a0ab7907191523f5a0528e3b9c288e21 f50733b45d865f91db90919f8311e2127ce5a0cb git Not specified
CNA Linux Linux affected 2.6.18 Not specified
CNA Linux Linux unaffected 2.6.18 semver Not specified
CNA Linux Linux unaffected 4.19.320 4.19.* semver Not specified
CNA Linux Linux unaffected 5.4.282 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.224 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.165 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.106 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.47 6.6.* semver Not specified
CNA Linux Linux unaffected 6.10.6 6.10.* semver Not specified
CNA Linux Linux unaffected 6.11 * original_commit_for_fix Not specified
ADP Siemens RUGGEDCOM RST2428P affected V3.1 custom Not specified
ADP Siemens RUGGEDCOM RST2428P unaffected * custom Not specified
ADP Siemens SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 Family unaffected * custom Not specified
ADP Siemens SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 Family unaffected * custom Not specified
ADP Siemens SCALANCE XCM-/XRM-/XCH-/XRH-300 Family affected V3.1 custom Not specified
ADP Siemens SCALANCE XCM-/XRM-/XCH-/XRH-300 Family unaffected * custom Not specified
ADP Siemens SIMATIC S7-1500 TM MFP - GNU/Linux Subsystem affected * custom Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/f6cfc6bcfd5e1cf76115b6450516ea4c99897ae1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
cert-portal.siemens.com/productcert/html/ssa-265688.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/368f6985d46657b8b466a421dddcacd4051f7ada 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/15469d46ba34559bfe7e3de6659115778c624759 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/90dfbba89ad4f0d9c9744ecbb1adac4aa2ff4f3e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
cert-portal.siemens.com/productcert/html/ssa-613116.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/d2a2a4714d80d09b0f8eb6438ab4224690b7121e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/f50733b45d865f91db90919f8311e2127ce5a0cb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2024/10/msg00003.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
cert-portal.siemens.com/productcert/html/ssa-355557.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/d5c3c7e26275a2d83b894d30f7582a42853a958f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/01/msg00001.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
git.kernel.org/stable/c/9b424c5d4130d56312e2a3be17efb0928fec4d64 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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