# CVE-2024-44939: jfs: fix null ptr deref in dtInsertEntry

> A null pointer dereference in the Linux kernel JFS filesystem allows local attackers to cause a system crash.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Aug 2024
- **Updated:** 5 Aug 2026
- **Also known as:** AZL-49075, BELL-CVE-2024-44939, DEBIAN-CVE-2024-44939, GHSA-27qw-rmpj-379q, ROOT-OS-DEBIAN-11-CVE-2024-44939, ROOT-OS-UBUNTU-2204-CVE-2024-44939, UBUNTU-CVE-2024-44939

## What is CVE-2024-44939?

CVE-2024-44939 is a high-severity vulnerability in Linux kernel, published on 26 Aug 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

jfs: fix null ptr deref in dtInsertEntry

[syzbot reported]
general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 PID: 5061 Comm: syz-executor404 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:dtInsertEntry+0xd0c/0x1780 fs/jfs/jfs_dtree.c:3713
...
[Analyze]
In dtInsertEntry(), when the pointer h has the same value as p, after writing
name in UniStrncpy_to_le(), p->header.flag will be cleared. This will cause the
previously true judgment "p->header.flag & BT-LEAF" to change to no after writing
the name operation, this leads to entering an incorrect branch and accessing the
uninitialized object ih when judging this condition for the second time.

[Fix]
After got the page, check freelist first, if freelist == 0 then exit dtInsert()
and return -EINVAL.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2024-44939?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-44939?

Apply the vendor's patch.

## Is CVE-2024-44939 being exploited?

There is no known exploitation of CVE-2024-44939 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-44939 and fix it if it is affected.

What it is: CVE-2024-44939 is a high-severity vulnerability in Linux kernel, published on 26 Aug 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-44939 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2024-44939/ (Markdown: https://insights.sbomify.com/CVE-2024-44939/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-44939
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-44939
- OSV: https://osv.dev/vulnerability/CVE-2024-44939

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-44939/
Summaries are generated and may contain mistakes; the official description above is the record.