CVSS 3.1
4.3 mediumCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:LCVE-2026-124740 Busybox: use-after-free of requested_ipv6 in udhcpc6
Medium (4.3) in red hat. EPSS 0.2% estimated probability of exploitation activity in the next 30 days.
On this page
A flaw was found in BusyBox's udhcpc6 DHCPv6 client. A malicious server on the local network can trigger a use-after-free condition by responding with a crafted Dynamic Host Configuration Protocol for IPv6 (DHCPv6) reply packet lacking usable address options. This issue causes the client to read stale heap memory, which can result in a Denial of Service (DoS) due to an application crash or disclose previously assigned network address data in subsequent discovery requests.
Severity
- EPSS
- 0.2% estimated probability of exploitation activity in the next 30 days; 10th percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
- CISA's assessment (SSVC)
- Exploitation: none · Automatable: no · Technical impact: partial, assessed 2026-11-12. From CISA's Vulnrichment in the CVE List: whether it is exploited, whether exploiting it can be automated, and how much control it gives.
- CWE
- CWE-416 Use After Free
- Published
- Modified
- Assigned by
- redhat (CNA)
- NVD analysis
- Awaiting analysis
- Record from
- the NVD, synced
Ask an AI about this CVE
Show the prompt
Explain CVE-2026-124740 for an engineer deciding whether to act. Use https://cve.bz/api/public/cves/CVE-2026-124740?via=ask-ai-copy and https://cve.bz/cve/CVE-2026-124740?via=ask-ai-copy as the source of truth: what is affected and which versions fix it, whether it is in CISA KEV, public exploits, and its EPSS (an internet-wide 30-day estimate of exploitation activity, not a forecast for my systems). If they give no fixed versions, use the CVE record https://cveawg.mitre.org/api/cve/CVE-2026-124740 or the vendor advisory, not third-party mirrors. Tell me how to check whether I am affected and how to verify a fix. Cite the sources and say where they are uncertain.Opens a third-party assistant; its answer is its own, not cve.bz's. The prompt holds only this CVE's id and public links.
Badge for a README or a site
An image that stays current: it is drawn from the data each time it is fetched (a host that proxies images, as GitHub does, may show its copy for a while). Markdown:
[](https://cve.bz/cve/CVE-2026-124740)
HTML:
<a href="https://cve.bz/cve/CVE-2026-124740"><img src="https://cve.bz/cve/badge/CVE-2026-124740.svg" alt="CVE-2026-124740"></a>
Affected
- red hat:red hat enterprise linux 6
- red hat:red hat hardened images
Linux distributions
| Distribution | Release | Package | Fixed in | Advisory |
|---|---|---|---|---|
| Ubuntu | 20.04:LTS, 22.04:LTS, 24.04:LTS and 5 more | busybox | no fix listed | UBUNTU-CVE-2026-124740 |
From the distributions' data via OSV.dev: Ubuntu Security Notices © Canonical Ltd., CC BY-SA 4.0. Modified: reformatted and linked to CVE records. Credits. On the distributions' own pages: Ubuntu.
Red Hat
Red Hat rates this Moderate.
This vulnerability is classified as Moderate severity because exploitation requires an adjacent attacker on the local network link to operate a rogue DHCPv6 server, and the impact is restricted to stale heap data disclosure in outbound packets or a client denial of service. BusyBox udhcpc6 is not deployed as the default DHCP client in standard Red Hat Enterprise Linux installations, which instead rely on NetworkManager. As a result, the risk is limited to custom environments, containers, or minimal recovery images where the BusyBox DHCPv6 client is specifically executed.
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 6 | busybox | Not affected | |
| Red Hat Hardened Images | busybox | Affected |
Contains Red Hat Security Data © Red Hat, Inc., licensed under CC BY 4.0. Source: https://access.redhat.com/security/data. Modified: reformatted. Red Hat's page for CVE-2026-124740.