fbdev: fix use-after-free in store_modes()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63826
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 12:16:55 UTC
Updated2026-07-20 07:16:40 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: fbdev: fix use-after-free in store_modes() store_modes() replaces a framebuffer's modelist with modes from userspace. On success it frees the old modelist with fb_destroy_modelist(). Two fields still point into that freed list. One pointer is fb_display[i].mode, the mode a console is using. fbcon_new_modelist() moves these pointers to the new list. It only does so for consoles still mapped to the framebuffer. An unmapped console is skipped and keeps its stale pointer. Unbinding fbcon, for example, sets con2fb_map[i] to -1 but leaves fb_display[i].mode set. An FBIOPUT_VSCREENINFO ioctl with FB_ACTIVATE_INV_MODE later reaches fbcon_mode_deleted(). That function reads the stale fb_display[i].mode through fb_mode_is_equal(). The read is a use-after-free. The other pointer is fb_info->mode, the current mode. It is set through the mode sysfs attribute. store_modes() does not update fb_info->mode, so it is left pointing into the freed list. show_mode(), the attribute's read handler, dereferences the stale fb_info->mode through mode_string(). The read is a use-after-free. Clear both pointers before freeing the list. Commit a1f305893074 ("fbcon: Set fb_display[i]->mode to NULL when the mode is released") added the helper fbcon_delete_modelist(). It clears every fb_display[i].mode that points into a given list. So far it is called only from the unregister path. Call it from store_modes() too, and set fb_info->mode to NULL.

Risk And Classification

EPSS: 0.001570000 probability, percentile 0.052660000 (date 2026-07-20)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 5267eab88fa4c684459504b8be577ad64953b9a6 git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 c6765f39ed27014ff877b00a2efa494233404e17 git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 0d35f9f194a858567a21017d69318a51e3a822b9 git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 70f1e000b88cfa8ca3fd7f4d082647fc089a7769 git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 2c1c805c65fb7dc7524e20376d6987721e73a0b1 git Not specified
CNA Linux Linux affected 2.6.12 Not specified
CNA Linux Linux unaffected 2.6.12 semver Not specified
CNA Linux Linux unaffected 6.6.144 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.95 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.38 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.3 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/c6765f39ed27014ff877b00a2efa494233404e17 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/5267eab88fa4c684459504b8be577ad64953b9a6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0d35f9f194a858567a21017d69318a51e3a822b9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2c1c805c65fb7dc7524e20376d6987721e73a0b1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/70f1e000b88cfa8ca3fd7f4d082647fc089a7769 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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