# CVE-2025-39735: jfs: fix slab-out-of-bounds read in ea_get()

> An integer overflow in the JFS filesystem allows out-of-bounds reads, potentially causing system crashes or leaking kernel memory.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/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:** 18 Apr 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-39735, DEBIAN-CVE-2025-39735, GHSA-rh6v-853j-mqjh, ROOT-OS-UBUNTU-2404-CVE-2025-39735, UBUNTU-CVE-2025-39735

## What is CVE-2025-39735?

CVE-2025-39735 is a high-severity vulnerability in Linux kernel, published on 18 Apr 2025. 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 slab-out-of-bounds read in ea_get()

During the "size_check" label in ea_get(), the code checks if the extended
attribute list (xattr) size matches ea_size. If not, it logs
"ea_get: invalid extended attribute" and calls print_hex_dump().

Here, EALIST_SIZE(ea_buf->xattr) returns 4110417968, which exceeds
INT_MAX (2,147,483,647). Then ea_size is clamped:

	int size = clamp_t(int, ea_size, 0, EALIST_SIZE(ea_buf->xattr));

Although clamp_t aims to bound ea_size between 0 and 4110417968, the upper
limit is treated as an int, causing an overflow above 2^31 - 1. This leads
"size" to wrap around and become negative (-184549328).

The "size" is then passed to print_hex_dump() (called "len" in
print_hex_dump()), it is passed as type size_t (an unsigned
type), this is then stored inside a variable called
"int remaining", which is then assigned to "int linelen" which
is then passed to hex_dump_to_buffer(). In print_hex_dump()
the for loop, iterates through 0 to len-1, where len is
18446744073525002176, calling hex_dump_to_buffer()
on each iteration:

	for (i = 0; i < len; i += rowsize) {
		linelen = min(remaining, rowsize);
		remaining -= rowsize;

		hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,
				   linebuf, sizeof(linebuf), ascii);

		...
	}

The expected stopping condition (i < len) is effectively broken
since len is corrupted and very large. This eventually leads to
the "ptr+i" being passed to hex_dump_to_buffer() to get closer
to the end of the actual bounds of "ptr", eventually an out of
bounds access is done in hex_dump_to_buffer() in the following
for loop:

	for (j = 0; j < len; j++) {
			if (linebuflen < lx + 2)
				goto overflow2;
			ch = ptr[j];
		...
	}

To fix this we should validate "EALIST_SIZE(ea_buf->xattr)"
before it is utilised.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2025-39735?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-39735?

Apply the vendor's patch.

## Is CVE-2025-39735 being exploited?

There is no known exploitation of CVE-2025-39735 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-2025-39735 and fix it if it is affected.

What it is: CVE-2025-39735 is a high-severity vulnerability in Linux kernel, published on 18 Apr 2025. 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-2025-39735 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-2025-39735/ (Markdown: https://insights.sbomify.com/CVE-2025-39735/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39735
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39735
- OSV: https://osv.dev/vulnerability/CVE-2025-39735

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39735/
Summaries are generated and may contain mistakes; the official description above is the record.