CVE-2026-74635: Linux kernel · fbdev: bitblit: bound-check glyph index in bit_cursor()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High · fixed in 5.15.0-1117.124~20.04.1 : patch Linux kernel soon.
Data as of 26 Oct 2026, 12:55 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.15.0-1117.124~20.04.1, 5.15.0-1123.132~20.04.1, 5.15.0-1122.131~20.04.1 +27
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 22 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
An official fix is available and should be applied. The vulnerability has been patched by adding proper bounds checking in the bit_cursor() function. Users should update their Linux kernel to a fixed version as provided by their distribution. No additional mitigation is required beyond applying the official patch.
Description
A vulnerability in the Linux kernel's framebuffer device (fbdev) bitblit code was fixed. The issue involves an out-of-bounds read in the bit_cursor() function due to insufficient bounds checking of the glyph index fetched from the screen buffer. This can occur when the font changes from one with 512 glyphs to one with 256 glyphs, leaving stale screen data with high bits set. The flaw was triggered by the vcs_write() function writing arbitrary 16-bit values without proper validation. The fix adds clamping of the glyph index to prevent out-of-bounds access without changing cursor behavior.
References
- nvd.nist.gov/vuln/detail/CVE-2026-74635 (opens in a new tab)
- git.kernel.org/stable/c/250159ace2dc53c1bdad267aa8da51b638748700 (opens in a new tab)
- git.kernel.org/stable/c/46336f476484f36145e5117e72d7b590f47433ee (opens in a new tab)
- git.kernel.org/stable/c/94134d70abf9273b70499d97d0adc9185ef21091 (opens in a new tab)
- git.kernel.org/stable/c/9ea879862e66e354e616028c31b39aa3eb6d35d8 (opens in a new tab)
- git.kernel.org/stable/c/bc9db0d879c655d5dfd8add32fd60f13e65d132c (opens in a new tab)
- git.kernel.org/stable/c/bf750cfeacf4e47ac72dadc7f05839696efb8576 (opens in a new tab)
- git.kernel.org/stable/c/c1e7351767dd30fc574395c82121e4c67b882da3 (opens in a new tab)
- git.kernel.org/stable/c/e033cbf3975a8465f879ebd5989dc35b04423a4d (opens in a new tab)
- ubuntu.com/security/CVE-2026-74635 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-74635 (opens in a new tab)
- msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-74635.json (opens in a new tab)
- support.microsoft.com/lifecycle (opens in a new tab)
- first.org/cvss (opens in a new tab)
- ubuntu.com/security/notices/USN-8878-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8879-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8877-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8886-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-2 (opens in a new tab)