# CVE-2025-37749: net: ppp: Add bound checking for skb data on ppp_sync_txmung

> A missing bounds check in the Linux kernel PPP driver allows out-of-bounds access when processing short packets, potentially leading to crashes or code execution.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 May 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-37749, DEBIAN-CVE-2025-37749, GHSA-v3g9-9rfh-r7cr, ROOT-OS-DEBIAN-12-CVE-2025-37749, ROOT-OS-UBUNTU-2204-CVE-2025-37749, ROOT-OS-UBUNTU-2404-CVE-2025-37749, UBUNTU-CVE-2025-37749

## What is CVE-2025-37749?

CVE-2025-37749 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 1 May 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

net: ppp: Add bound checking for skb data on ppp_sync_txmung

Ensure we have enough data in linear buffer from skb before accessing
initial bytes. This prevents potential out-of-bounds accesses
when processing short packets.

When ppp_sync_txmung receives an incoming package with an empty
payload:
(remote) gef➤  p *(struct pppoe_hdr *) (skb->head + skb->network_header)
$18 = {
	type = 0x1,
	ver = 0x1,
	code = 0x0,
	sid = 0x2,
        length = 0x0,
	tag = 0xffff8880371cdb96
}

from the skb struct (trimmed)
      tail = 0x16,
      end = 0x140,
      head = 0xffff88803346f400 "4",
      data = 0xffff88803346f416 ":\377",
      truesize = 0x380,
      len = 0x0,
      data_len = 0x0,
      mac_len = 0xe,
      hdr_len = 0x0,

it is not safe to access data[2].

[pabeni@redhat.com: fixed subj typo]

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

## Which versions are affected by CVE-2025-37749?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-37749?

Apply the vendor's patch.

## Is CVE-2025-37749 being exploited?

There is no known exploitation of CVE-2025-37749 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-37749 and fix it if it is affected.

What it is: CVE-2025-37749 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 1 May 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-37749 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2025-37749/ (Markdown: https://insights.sbomify.com/CVE-2025-37749/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-37749
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-37749
- OSV: https://osv.dev/vulnerability/CVE-2025-37749

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-37749/
Summaries are generated and may contain mistakes; the official description above is the record.