CVE-2021-21257

What it is

Contiki-NG is an open-source, cross-platform operating system for internet of things devices. The RPL-Classic and RPL-Lite implementations in the Contiki-NG operating system versions prior to 4.6 do not validate the address pointer in the RPL source routing header This makes it possible for an attacker to cause out-of-bounds writes with packets injected into the network stack. Specifically, the problem lies in the rpl_ext_header_srh_update function in the two rpl-ext-header.c modules for RPL-Classic and RPL-Lite respectively. The addr_ptr variable is calculated using an unvalidated CMPR field value from the source routing header. An out-of-bounds write can be triggered on line 151 in os/net/routing/rpl-lite/rpl-ext-header.c and line 261 in os/net/routing/rpl-classic/rpl-ext-header.c, which contain the following memcpy call with addr_ptr as destination. The problem has been patched in Contiki-NG 4.6. Users can apply a patch out-of-band as a workaround.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data tampering.

Exploit odds

1.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-06-18 21:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:35 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.1% in the next 30 days (EPSS).
• Severity: 8.2 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-06-18 21:15 UTC

Last modified

2026-06-17 03:35 UTC

Exploit probability

1.1% · EPSS, next 30 days

Weakness

CWE-787 · Out-of-bounds write

Record status

Modified

Affected

• contiki-ng < 4.6

Attack profile CVSS 3.1 · 8.2

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

Low

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-21257.md and follow it. Check whether this project is affected by CVE-2021-21257. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge