# CVE-2026-49868: RIOT DHCPv6 client out-of-bounds heap read

Source: https://junglewise.ai/threats/cve-2026-49868-riot-is-an-open-source-microcontroller-operating-system-designed  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-16. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-49868 · Severity: critical · CVSS 9.8 · Published 2026-10-16

RIOT is an open-source operating system for Internet of Things and embedded microcontroller devices. A malicious or compromised DHCPv6 server can send specially crafted network packets that cause the DHCPv6 client to read beyond allocated memory, potentially crashing devices and exposing sensitive data stored in memory.

Technologies: [Riot-Os Riot](https://junglewise.ai/threats/technologies/riot). Vendors: [Riot-Os](https://junglewise.ai/threats/vendors/riot-os).

## Quick answers

**Is CVE-2026-49868 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-49868 being exploited in the wild.

**How severe is CVE-2026-49868?** Critical severity, with a CVSS score of 9.8, published 16 October 2026.

**Which products and versions are affected?** Riot-Os Riot before 2026.07.

**Is there a fix for CVE-2026-49868?** Yes: fixed in 2026.07. Until then: Disable MODULE_DHCPV6_CLIENT_IA_PD if DHCPv6 is not required, or restrict network access to trusted DHCPv6 servers only. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-49868 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-49868?** Check whether you run Riot-Os Riot at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 2026.07

Disable MODULE_DHCPV6_CLIENT_IA_PD if DHCPv6 is not required, or restrict network access to trusted DHCPv6 servers only.

## Technical details

The _parse_reply() function in the DHCPv6 client omits validation of minimum option length before passing IA_PD and IA_NA option bodies to sub-option parsers. When MODULE_DHCPV6_CLIENT_IA_PD is enabled, a malicious REPLY with an option length smaller than the required structure causes size_t underflow in _parse_ia_pd_option(), leading to unbounded out-of-bounds heap reads. The vulnerability requires network access to a DHCPv6 server and is fixed by checking option length against sizeof(dhcpv6_opt_ia_pd_t) before parsing.

## Affected products

- RIOT-OS RIOT before 2026.07

## Timeline

- 2026-10-16: disclosed
- 2026-05-27: patched

## References

- [https://github.com/RIOT-OS/RIOT/commit/c9830dc5f2a9bf97418de4fc7d7167d00a45df17](https://github.com/RIOT-OS/RIOT/commit/c9830dc5f2a9bf97418de4fc7d7167d00a45df17)
- [https://github.com/RIOT-OS/RIOT/pull/22322](https://github.com/RIOT-OS/RIOT/pull/22322)

## Related threats

- [RIOT nanocoap integer overflow in Block2 option parsing](https://junglewise.ai/threats/cve-2026-102692-riot-is-an-open-source-microcontroller-operating-system-designed)
- [RIOT nanocoap_fileserver assertion failure in response handling](https://junglewise.ai/threats/cve-2026-107838-riot-is-an-open-source-microcontroller-operating-system-designed)
- [RIOT operating system out-of-bounds read in 6LoWPAN fragment handling](https://junglewise.ai/threats/cve-2026-107837-riot-is-an-open-source-microcontroller-operating-system-designed)
- [RIOT nanoCoAP client buffer underflow in blockwise transfer](https://junglewise.ai/threats/cve-2026-107836-riot-is-an-open-source-microcontroller-operating-system-designed)
- [RIOT OS stack overflow in ethos serial frame parser](https://junglewise.ai/threats/cve-2026-22214-riot-os-stack-overflow-in-ethos-serial-frame-parser)