CVE-2024-42305: Linux kernel · ext4: check dot and dotdot of dx_root before making dir indexed
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium · fixed in 5.4.0-1135.145~18.04.1 : update Linux kernel when convenient.
Data as of 26 Oct 2026, 23:28 UTC
- Patch
- Available – fixed in 5.4.0-1135.145~18.04.1, 5.4.0-1140.147~18.04.1, 5.4.0-1139.148~18.04.1 +75
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 17 Aug 2024
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.
Patches and advisories
- ubuntu.com/security/notices/USN-7088-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7100-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7100-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-7119-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7123-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7144-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7154-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7155-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gkeoppkg:deb/ubuntu/linux-gkeop?arch=source&distro=nobleOther 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: ext4: check dot and dotdot of dx_root before making dir indexed Syzbot reports a issue as follows: ============================================ BUG: unable to handle page fault for address: ffffed11022e24fe PGD 23ffee067 P4D 23ffee067 PUD 0 Oops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 0 PID: 5079 Comm: syz-executor306 Not tainted 6.10.0-rc5-g55027e689933 #0 Call Trace: <TASK> make_indexed_dir+0xdaf/0x13c0 fs/ext4/namei.c:2341 ext4_add_entry+0x222a/0x25d0 fs/ext4/namei.c:2451 ext4_rename fs/ext4/namei.c:3936 [inline] ext4_rename2+0x26e5/0x4370 fs/ext4/namei.c:4214 [...] ============================================ The immediate cause of this problem is that there is only one valid dentry for the block to be split during do_split, so split==0 results in out of bounds accesses to the map triggering the issue. do_split unsigned split dx_make_map count = 1 split = count/2 = 0; continued = hash2 == map[split - 1].hash; ---> map[4294967295] The maximum length of a filename is 255 and the minimum block size is 1024, so it is always guaranteed that the number of entries is greater than or equal to 2 when do_split() is called. But syzbot's crafted image has no dot and dotdot in dir, and the dentry distribution in dirblock is as follows: bus dentry1 hole dentry2 free |xx--|xx-------------|...............|xx-------------|...............| 0 12 (8+248)=256 268 256 524 (8+256)=264 788 236 1024 So when renaming dentry1 increases its name_len length by 1, neither hole nor free is sufficient to hold the new dentry, and make_indexed_dir() is called. In make_indexed_dir() it is assumed that the first two entries of the dirblock must be dot and dotdot, so bus and dentry1 are left in dx_root because they are treated as dot and dotdot, and only dentry2 is moved to the new leaf block. That's why count is equal to 1. Therefore add the ext4_check_dx_root() helper function to add more sanity checks to dot and dotdot before starting the conversion to avoid the above issue.
References
- ubuntu.com/security/CVE-2024-42305 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2024-42305 (opens in a new tab)
- git.kernel.org/linus/50ea741def587a64e08879ce6c6a30131f7111e7 (opens in a new tab)
- git.kernel.org/stable/c/abb411ac991810c0bcbe51c2e76d2502bf611b5c (opens in a new tab)
- git.kernel.org/stable/c/9d241b7a39af192d1bb422714a458982c7cc67a2 (opens in a new tab)
- git.kernel.org/stable/c/cdd345321699042ece4a9d2e70754d2397d378c5 (opens in a new tab)
- git.kernel.org/stable/c/50ea741def587a64e08879ce6c6a30131f7111e7 (opens in a new tab)
- git.kernel.org/stable/c/b80575ffa98b5bb3a5d4d392bfe4c2e03e9557db (opens in a new tab)
- git.kernel.org/stable/c/19e13b4d7f0303186fcc891aba8d0de7c8fdbda8 (opens in a new tab)
- git.kernel.org/stable/c/42d420517072028fb0eb852c358056b7717ba5aa (opens in a new tab)
- git.kernel.org/stable/c/8afe06ed3be7a874b3cd82ef5f8959aca8d6429a (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7100-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7100-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7088-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-7119-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7123-1 (opens in a new tab)