CVE-2020-17438: An issue was discovered in uIP 1.0, as used in Contiki 3.0 and other products

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CRITICAL 9.8REMOTEDOWNGRADE

CVE-2020-17438 is a critical-severity flaw (CVSS 9.8) affecting uip. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in uIP 1.0, as used in Contiki 3.0 and other products. The code that reassembles fragmented packets fails to properly validate the total length of an incoming packet specified in its IP header, as well as the fragmentation offset value specified in the IP header. By crafting a packet with specific values of the IP header length and the fragmentation offset, attackers can write into the .bss section of the program (past the

Why this priority

Critical severity
EPSS top 3%: very likely to be exploited
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	19.3% (top 3%)
CISA exploited list	No
Weakness	CWE-787
Published	2020-12-11
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: uip project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-12-11 23:15 UTCPublished CVE record published
2026-06-17 02:58 UTCUpdated Record last modified

uip project uip DOWNGRADE

Affected: 1.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0

1. Check installed version

apt-cache policy uip || rpm -q uip || uip --version

2. No fixed release: DOWNGRADE to a release before 1.0 (Debian / Ubuntu)

apt-cache madison uip sudo apt install uip=<VERSION_BEFORE_1.0> sudo apt-mark hold uip

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list uip sudo dnf downgrade uip-<VERSION_BEFORE_1.0> sudo dnf versionlock add uip

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-17438?

uip: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-17438 being exploited?

CVE-2020-17438 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-17438 affect?

CVE-2020-17438 affects uip. Severity is critical (CVSS 9.8). An issue was discovered in uIP 1.0, as used in Contiki 3.0 and other products. The code that reassembles fragmented packets fails to properly validate the total length of an incoming packet specified in its IP header, as well as the fragmen

How urgent is CVE-2020-17438?

Priority 64/100. Critical severity; EPSS top 3%: very likely to be exploited; Remotely exploitable, no login, no user action

Related CVEs

CVE-2020-24335 HIGH 7.5 UPGRADE An issue was discovered in uIP through 1.0, as used in Contiki and Contiki-NG
CVE-2020-24334 HIGH 8.2 UPGRADE The code that processes DNS responses in uIP through 1.0, as used in Contiki and Contiki-NG, does not check wh
CVE-2020-17440 HIGH 7.5 DOWNGRADE An issue was discovered in uIP 1.0, as used in Contiki 3.0 and other products
CVE-2020-17439 HIGH 8.3 DOWNGRADE An issue was discovered in uIP 1.0, as used in Contiki 3.0 and other products
CVE-2020-17437 HIGH 8.2 UPGRADE UPGRADE An issue was discovered in uIP 1.0, as used in Contiki 3.0 and other products

References

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