# CVE-2026-124740: Busybox: use-after-free of requested_ipv6 in udhcpc6

Status: published. Published: 2026-11-11. Updated: 2026-11-12.

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.

## Remediation

- workaround: 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. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 6 (busybox): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Hardened Images (busybox): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 4.3 (medium); CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L; source: CNA: redhat

- CVSS 3.1: 4.3 (medium); CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L; source: NVD: secalert@redhat.com

- CISA KEV: No listing in collected sources

- EPSS: 0.20% as of 2026-11-12; percentile 10.35%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-416

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/security/cve/CVE-2026-124740 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2571616 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-124740 (secalert@redhat.com)

- https://bugzilla.redhat.com/show_bug.cgi?id=2571616 (secalert@redhat.com)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-124740; retrieved 2026-11-12; source updated 2026-11-12

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-124740; retrieved 2026-11-11; source updated 2026-11-11

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-124740; retrieved 2026-11-12; source updated Not reported

Revision: 0be9307f15a9a95ac222570194560bfe9d68744d79b42f449bed8381076b9ba9

Canonical: https://y2.dev/cve/CVE-2026-124740

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