How severe is CVE-2021-3635?

CVE-2021-3635 has a CVSS 3.x base score of 4.4, rated medium severity. It is exploitable over local access with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-3635 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3635?

CVE-2021-3635 primarily affects Redhat Enterprise Linux. In total, 11 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-3635?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-3635 published?

CVE-2021-3635 was published on 2021-08-13 and last updated on 2026-06-17.

CVE-2021-3635

CVE-2021-3635 is a medium-severity vulnerability in Redhat Enterprise Linux with a CVSS 3.x base score of 4.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-119.

Key facts

Severity: Medium (CVSS 3.x base score 4.4)
CVSS v2: 4.9
EPSS exploit prediction: 0% (15th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-119
Affected product: Redhat Enterprise Linux
Published: 2021-08-13
Last modified: 2026-06-17

Description

A flaw was found in the Linux kernel netfilter implementation in versions prior to 5.5-rc7. A user with root (CAP_SYS_ADMIN) access is able to panic the system when issuing netfilter netflow commands.

Frequently asked questions

What is CVE-2021-3635?: A flaw was found in the Linux kernel netfilter implementation in versions prior to 5.5-rc7. A user with root (CAP_SYS_ADMIN) access is able to panic the system when issuing netfilter netflow commands.
How severe is CVE-2021-3635?: CVE-2021-3635 has a CVSS 3.x base score of 4.4, rated medium severity. It is exploitable over local access with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-3635 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3635?: CVE-2021-3635 primarily affects Redhat Enterprise Linux. In total, 11 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-3635?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-3635 published?: CVE-2021-3635 was published on 2021-08-13 and last updated on 2026-06-17.

References

https://bugzilla.redhat.com/show_bug.cgi?id=1976946

Affected products (11)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.5:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.5:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.5:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.5:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.5:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.5:rc6:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux:6.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux:7.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

More vulnerabilities in Redhat Enterprise Linux

CVE-2015-0240 — Critical (CVSS 10.0): The Netlogon server implementation in smbd in Samba 3.5.x and 3.6.x before 3.6.25, 4.0.x before 4.0.25, 4.1.x before…
CVE-2015-0408 — Critical (CVSS 10.0): Unspecified vulnerability in Oracle Java SE 5.0u75, 6u85, 7u72, and 8u25 allows remote attackers to affect…
CVE-2014-6601 — Critical (CVSS 10.0): Unspecified vulnerability in Oracle Java SE 6u85, 7u72, and 8u25 allows remote attackers to affect confidentiality,…
CVE-2009-0846 — Critical (CVSS 10.0): The asn1_decode_generaltime function in lib/krb5/asn.1/asn1_decode.c in the ASN.1 GeneralizedTime decoder in MIT…
CVE-2007-1007 — Critical (CVSS 10.0): Format string vulnerability in GnomeMeeting 1.0.2 and earlier allows remote attackers to cause a denial of service…
CVE-2006-6235 — Critical (CVSS 10.0): A "stack overwrite" vulnerability in GnuPG (gpg) 1.x before 1.4.6, 2.x before 2.0.2, and 1.9.0 through 1.9.95 allows…

All CVEs affecting Redhat Enterprise Linux →

Other CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) vulnerabilities

CVE-2026-2778 — Critical (CVSS 10.0): Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component. This vulnerability was fixed in…
CVE-2026-2776 — Critical (CVSS 10.0): Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability…
CVE-2025-1866 — Critical (CVSS 10.0): Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability in warmcat libwebsockets allows…
CVE-2022-27625 — Critical (CVSS 10.0): A vulnerability regarding improper restriction of operations within the bounds of a memory buffer is found in the…
CVE-2022-27624 — Critical (CVSS 10.0): A vulnerability regarding improper restriction of operations within the bounds of a memory buffer is found in the…
CVE-2020-11896 — Critical (CVSS 10.0): The Treck TCP/IP stack before 6.0.1.66 allows Remote Code Execution, related to IPv4 tunneling.

Browse all CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) vulnerabilities →