What’s Vulnerable › Vulnerabilities

CVE-2021-20177

• Severity: medium (CVSS 4.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-05-26 · updated 2026-06-17
• Weakness: CWE-125

Description

A flaw was found in the Linux kernel's implementation of string matching within a packet. A privileged user (with root or CAP_NET_ADMIN) when inserting iptables rules could insert a rule which can panic the system. Kernel before kernel 5.5-rc1 is affected.

Affected products

• Linux kernel: through 5.4.9

References

• https://bugzilla.redhat.com/show_bug.cgi?id=1914719
• https://bugzilla.redhat.com/show_bug.cgi?id=1914719

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