CVE-2026-124740 Busybox: use-after-free of requested_ipv6 in udhcpc6
A malicious local network DHCPv6 server can crash BusyBox udhcpc6 clients or leak address data via crafted replies.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Harmful if only installed
- No
- Needs a specific call
- No
- Fix
- None listed
What is CVE-2026-124740?
CVE-2026-124740 is a medium-severity use after free vulnerability in Red Hat Enterprise Linux 6, published on 11 Nov 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-416
Which versions are affected by CVE-2026-124740?
An affected version is exposed as installed. No special setting or call is needed.
How do I fix CVE-2026-124740?
No fix has been published for CVE-2026-124740 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-124740 being exploited?
There is no known exploitation of CVE-2026-124740 in the wild and no public exploit code.
Sources
Also known as GHSA-9f82-ccff-m2qq.