CVE-2026-89787: Linux kernel · ext4: check dir entry fits before reading the hash trailer in ext4_search_dir()
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 26 Oct 2026, 17:16 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Exploitation evidence
Disclosed: evidence found.
CVE published 16 Sep 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
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
A fix is available that enforces proper bounds checking of directory entries including the hash trailer before ext4_match() is called. Users should apply the updated Linux kernel versions that include this patch. No additional mitigations are indicated or required beyond applying the official fix.
Description
A vulnerability in the Linux kernel's ext4 filesystem was resolved involving improper bounds checking before reading a hash trailer in ext4_search_dir(). This flaw allows an out-of-bounds read when a crafted directory entry ends exactly at a block boundary, causing ext4_match() to read past the block end. The issue is detected by KASAN as a use-after-free error. The fix requires verifying that the entire directory entry, including the hash trailer, fits within the block before calling ext4_match().
References
- ubuntu.com/security/CVE-2026-89787 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-89787 (opens in a new tab)
- git.kernel.org/linus/c7e6b863d298f56522d0d08554bbea7f142e6588 (opens in a new tab)
- git.kernel.org/stable/c/3933884bc3102898b458c53fbd1ac52eb9cdb8a4 (opens in a new tab)
- git.kernel.org/stable/c/4d20106c536b73c4a8a02652dc85e35898baebf7 (opens in a new tab)
- git.kernel.org/stable/c/61a395967de06edba58760e81907a272db749faa (opens in a new tab)
- git.kernel.org/stable/c/83663c0b739480c00cfe785675db87520ec484ed (opens in a new tab)
- git.kernel.org/stable/c/c7e6b863d298f56522d0d08554bbea7f142e6588 (opens in a new tab)
- git.kernel.org/stable/c/d8c184bec24b5a00ae96d704856d935eaded1685 (opens in a new tab)
- git.kernel.org/stable/c/e94676a08af6312aa72d8a981232b281f9bcfcf5 (opens in a new tab)
- msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-89787.json (opens in a new tab)
- support.microsoft.com/lifecycle (opens in a new tab)
- first.org/cvss (opens in a new tab)