Raw vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2026-42512 is a high-severity Heap-based Buffer Overflow (CWE-122) vulnerability in Freebsd Freebsd. Its CVSS base score is 8.1 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 30% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-42512 is a heap buffer overrun vulnerability (CWE-122) affecting dhclient, the DHCP client daemon in FreeBSD. The flaw arises when dhclient constructs an environment array of string pointers to pass to dhclient-script and must resize it. The code miscalculates the new array size during memory allocation, resulting in a heap buffer overrun. This vulnerability was published on 2026-04-30.
A remote, unauthenticated attacker can trigger the issue by sending a specially crafted DHCP packet, causing dhclient to overrun its buffer of environment entries. Exploitation leads to a denial-of-service condition through a crash of the dhclient process. Under certain conditions, the buffer overrun may be leveraged for remote code execution. The CVSS v3.1 base score is 8.1 (AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H), reflecting network accessibility, high attack complexity, and high impact on confidentiality, integrity, and availability.
The FreeBSD Security Advisory FreeBSD-SA-26:15.dhclient details mitigation measures and available patches, accessible at https://security.freebsd.org/advisories/FreeBSD-SA-26:15.dhclient.asc.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-26357
Vulnerability Data
As dhclient is building an environment to pass to dhclient-script, it may need to resize the array of string pointers. The code which expands the array incorrectly calculates its new size when requesting memory, resulting in a heap buffer overrun.…
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A specially crafted packet can cause dhclient to overrun its buffer of environment entries. This can result in a crash, but it may be possible to leverage this bug to achieve remote code execution.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.4.1
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation (including fuzzing and memory-error detectors) can discover heap overflows after they have been coded.
Input validation enforces bounds checking on data written to heap buffers, directly stopping the overflow condition from being introduced.
Security engineering principles require use of memory-safe constructs and bounds-checked allocation routines that avoid introducing heap overflows.
Memory-protection mechanisms limit the ability of a heap overflow to execute attacker-controlled code or corrupt adjacent structures.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure-development practices directly require bounds checking and safe memory handling that prevent heap overflows.
Vulnerability scanning and recording can discover heap-overflow flaws but does not prevent their introduction in code.
Timely patching removes known heap-overflow instances after they exist.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development and acceptance can detect heap overflows before release.
Secure development lifecycle mandates practices that reduce the likelihood of introducing heap overflows.
Application security requirements can specify bounds-checking and safe memory APIs that mitigate heap overflows.
Secure architecture and engineering principles include memory-safety and input-validation controls that address heap overflows.
Secure coding standards directly prescribe techniques (safe functions, bounds checks) that prevent heap-based buffer overflows.
Change management ensures controlled deployment of fixes for discovered heap-overflow vulnerabilities.