CVE-2021-23270: In Gargoyle OS 1.12.0, when IPv6 is used, a routing loop can occur that generates excessive network traffic be

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HIGH 7.5REMOTEDOWNGRADE

CVE-2021-23270 is a high-severity flaw (CVSS 7.5) affecting gargoyle. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In Gargoyle OS 1.12.0, when IPv6 is used, a routing loop can occur that generates excessive network traffic between an affected device and its upstream ISP's router. This occurs when a link prefix route points to a point-to-point link, a destination IPv6 address belongs to the prefix and is not a local IPv6 address, and a router advertisement is received with at least one global unique IPv6 prefix for which the on-link flag is set.

Why this priority

High severity
Remotely exploitable, no login, no user action

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

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.0% (top 36%)
CISA exploited list	No
Weakness	CWE-834
Published	2021-04-12
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: gargoyle-router

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

Am I affected?

Timeline

2021-04-12 19:15 UTCPublished CVE record published
2026-06-17 03:38 UTCUpdated Record last modified

gargoyle-router gargoyle DOWNGRADE

Affected: 1.12.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.12.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.12.0 (Debian / Ubuntu)

apt-cache madison gargoyle sudo apt install gargoyle=<VERSION_BEFORE_1.12.0> sudo apt-mark hold gargoyle

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

dnf --showduplicates list gargoyle sudo dnf downgrade gargoyle-<VERSION_BEFORE_1.12.0> sudo dnf versionlock add gargoyle

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-2021-23270?

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

Is CVE-2021-23270 being exploited?

CVE-2021-23270 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-2021-23270 affect?

CVE-2021-23270 affects gargoyle. Severity is high (CVSS 7.5). In Gargoyle OS 1.12.0, when IPv6 is used, a routing loop can occur that generates excessive network traffic between an affected device and its upstream ISP's router. This occurs when a link prefix route points to a point-to-point link, a de

How urgent is CVE-2021-23270?

Priority 47/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2010-3359 MEDIUM 4.8 UPGRADE MITIGATE If LD_LIBRARY_PATH is undefined in gargoyle-free before 2009-08-25, the variable will point to the current dir

References

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