Bug 2531347 (CVE-2026-88833)

Summary: CVE-2026-88833 busybox: busybox: udhcpc integer underflow in DHCP packet length calculation causes denial of service
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedCC: security-response-team
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in BusyBox's udhcpc DHCP client. When processing raw DHCP packets, the client replaces the validated packet length with an attacker-controlled value from the IP header without re-validating the minimum size. This leads to an integer underflow when subtracting header sizes, causing a subsequent memory copy with a massively oversized length. An attacker on the same network segment can send a specially crafted packet to crash the DHCP client, resulting in denial of service and loss of network connectivity.
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Description OSIDB Bzimport 2026-09-10 09:47:03 UTC 
A vulnerability was found in the BusyBox DHCP client (networking/udhcp/dhcpc.c), specifically in d4_recv_raw_packet(). The function trusts the attacker-controlled IP tot_len field to calculate the payload size. When a malicious DHCP packet is sent with IP tot_len set to 20, the subtraction underflows to a negative value, wraps to a massive unsigned value, and is passed to memcpy(), causing an immediate segfault.

Remote code execution is not practical because the oversized memcpy faults immediately. The attack requires Layer 2 network adjacency.