CVE-2024-26798: Linux kernel · fbcon: always restore the old font data in fbcon_do_set_font()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium · fixed in 5.15.0-1063.69~20.04.1 : update Linux kernel when convenient.
Data as of 12 Nov 2026, 18:50 UTC
- Patch
- Available – fixed in 5.15.0-1063.69~20.04.1, 5.15.0-1065.74~20.04.1, 5.15.0-1062.70~20.04.1 +42
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 4 Apr 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 12 Nov 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-6820-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6821-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6821-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-6828-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6820-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-6821-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-6821-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-6871-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6892-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6895-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6895-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-6900-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu Pro Realtime 24.04 LTSlinux-raspi-realtimepkg:deb/ubuntu/linux-raspi-realtime?arch=source&distro=realtime/nobleOther threats | Affected
| Fixed in
|
Ubuntu 22.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=jammyOther threats | Affected
| Fixed in
|
Ubuntu 22.04 LTSlinux-allwinner-5.19pkg:deb/ubuntu/linux-allwinner-5.19?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=jammyOther threats | Affected
| Fixed in
|
Ubuntu 22.04 LTSlinux-aws-5.19pkg:deb/ubuntu/linux-aws-5.19?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSlinux-aws-6.2pkg:deb/ubuntu/linux-aws-6.2?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
In the Linux kernel, the following vulnerability has been resolved: fbcon: always restore the old font data in fbcon_do_set_font() Commit a5a923038d70 (fbdev: fbcon: Properly revert changes when vc_resize() failed) started restoring old font data upon failure (of vc_resize()). But it performs so only for user fonts. It means that the "system"/internal fonts are not restored at all. So in result, the very first call to fbcon_do_set_font() performs no restore at all upon failing vc_resize(). This can be reproduced by Syzkaller to crash the system on the next invocation of font_get(). It's rather hard to hit the allocation failure in vc_resize() on the first font_set(), but not impossible. Esp. if fault injection is used to aid the execution/failure. It was demonstrated by Sirius: BUG: unable to handle page fault for address: fffffffffffffff8 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD cb7b067 P4D cb7b067 PUD cb7d067 PMD 0 Oops: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 8007 Comm: poc Not tainted 6.7.0-g9d1694dc91ce #20 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:fbcon_get_font+0x229/0x800 drivers/video/fbdev/core/fbcon.c:2286 Call Trace: <TASK> con_font_get drivers/tty/vt/vt.c:4558 [inline] con_font_op+0x1fc/0xf20 drivers/tty/vt/vt.c:4673 vt_k_ioctl drivers/tty/vt/vt_ioctl.c:474 [inline] vt_ioctl+0x632/0x2ec0 drivers/tty/vt/vt_ioctl.c:752 tty_ioctl+0x6f8/0x1570 drivers/tty/tty_io.c:2803 vfs_ioctl fs/ioctl.c:51 [inline] ... So restore the font data in any case, not only for user fonts. Note the later 'if' is now protected by 'old_userfont' and not 'old_data' as the latter is always set now. (And it is supposed to be non-NULL. Otherwise we would see the bug above again.)
References
- ubuntu.com/security/CVE-2024-26798 (opens in a new tab)
- git.kernel.org/stable/c/20a4b5214f7bee13c897477168c77bbf79683c3d (opens in a new tab)
- git.kernel.org/stable/c/2f91a96b892fab2f2543b4a55740c5bee36b1a6b (opens in a new tab)
- git.kernel.org/stable/c/73a6bd68a1342f3a44cac9dffad81ad6a003e520 (opens in a new tab)
- git.kernel.org/stable/c/a2c881413dcc5d801bdc9535e51270cc88cb9cd8 (opens in a new tab)
- git.kernel.org/stable/c/00d6a284fcf3fad1b7e1b5bc3cd87cbfb60ce03f (opens in a new tab)
- cve.org/CVERecord?id=CVE-2024-26798 (opens in a new tab)
- ubuntu.com/security/notices/USN-6820-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6821-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6821-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-6828-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6820-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-6821-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-6821-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-6871-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6892-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6895-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6895-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-6900-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-6895-3 (opens in a new tab)