Is CVE-2021-21257 in the CISA KEV catalog?

No. CVE-2021-21257 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-21257?

CVE-2021-21257 has a CVSS v3 base score of 8.2 (HIGH).

What is the EPSS score for CVE-2021-21257?

CVE-2021-21257 has an EPSS score of 1.09% (61th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-21257?

Upgrade contiki-ng to 4.6 or later.

CVE & CISA-KEV Catalog

CVE-2021-21257

HIGH

8.2

CVSS v3

NVD

Description

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.

CWE-787Out-of-bounds Write

How to fix

Remediation Available

contiki-ngNVD

Affected:< 4.6Fixed in:4.6CVE-2021-21257derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityHigh

AvailabilityLow

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L

Exploit Intelligence

1.09%probability of exploitation in 30 days

61stpercentile

Moderate risk: more likely to be exploited than 61% of all known CVEs.

References

Patch2

Related Vulnerabilities

Other CWE-787 (Out-of-bounds Write) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-22457	Critical	9.0	100%	KEV + Ransom	Fix
CVE-2025-0282	Critical	9.0	100%	KEV + Ransom	-
CVE-2015-3113	Critical	9.8	100%	KEV	Fix
CVE-2021-20038	Critical	9.8	100%	KEV + Ransom	-
CVE-2023-4863	High	8.8	100%	KEV	Fix
CVE-2020-16040	Medium	6.5	100%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.