binfmt_misc: don't let an 'F' entry pin its own instance

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74484
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-15 13:17:53 UTC
Updated2026-08-15 13:17:53 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: binfmt_misc: don't let an 'F' entry pin its own instance An entry registered with 'F' opens its interpreter at registration time and holds that file until the entry is freed. Any entry nobody removes by hand only gets closed once the binfmt_misc superblock is shut down. If the interpreter lives on a mount that keeps that superblock alive the two pin each other: binfmt_misc sb -> inode -> entry -> interp_file -> vfsmount -> binfmt_misc sb TL;DR the file is never closed. Once the mount namespace is gone there is nothing left to unregister through either. There are two ways to trigger this bug: - Point the interpreter at the instance itself. Its files are regular files owned by the mounter and both bm_get_inode() and simple_fill_super() leave i_op at empty_iops. So notify_change() falls back to simple_setattr() and chmod +x works. We never set SB_I_NOEXEC and so open_exec() accepts it. - Use the instance as an overlayfs lower layer. The overlay superblock holds a clone_private_mount() of every layer until it is destroyed and that clone is in no namespace. So umount_tree() never reaches it. That's a DoS. And it isn't only the superblock that leaks. It pins the user namespace it was mounted in, so every iteration permanently eats one of the caller's user namespace charges. So let's just do the sane thing. SB_I_NOEXEC makes open_exec() fail on the instance's own files and s_stack_depth makes overlayfs reject the layer before it ever takes a clone. That also covers the ecryptfs and fuse passthrough variants. What 'F' promises is unchanged. The stable tag is narrower than the Fixes tags on purpose. Before sandboxed mounts this needed global root against the single instance everyone shares, and the change doesn't apply to those trees anyway. Note that SB_I_NODEV is implicitly raised for userns mounts but raise it explicitly here as well.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 948b701a607f123df92ed29084413e5dd8cda2ed 1cc2decee06acc939337304e9b3f737fd5d8c4bd git Not specified
CNA Linux Linux affected 948b701a607f123df92ed29084413e5dd8cda2ed 4dad8ca637d44d5a6d5c23fa80c9e2e455198c2b git Not specified
CNA Linux Linux affected 948b701a607f123df92ed29084413e5dd8cda2ed 098e92fe0f1bde5af99c8cf504f13f01ef139f85 git Not specified
CNA Linux Linux affected 948b701a607f123df92ed29084413e5dd8cda2ed 79055d82772b9584f259b747fe40ff56a076678d git Not specified
CNA Linux Linux affected 4.8 Not specified
CNA Linux Linux unaffected 4.8 semver Not specified
CNA Linux Linux unaffected 6.12.103 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.44 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.8 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc6 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/4dad8ca637d44d5a6d5c23fa80c9e2e455198c2b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1cc2decee06acc939337304e9b3f737fd5d8c4bd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/79055d82772b9584f259b747fe40ff56a076678d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/098e92fe0f1bde5af99c8cf504f13f01ef139f85 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

© CVE.report 2026

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

Free CVE JSON API cve.report/api

CVE.report and Source URL Uptime Status status.cve.report