How severe is CVE-2021-41611?

CVE-2021-41611 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-41611 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-41611?

CVE-2021-41611 primarily affects Squid-cache Squid. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-41611?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-41611 published?

CVE-2021-41611 was published on 2021-10-18 and last updated on 2026-06-17.

CVE-2021-41611

CVE-2021-41611 is a high-severity vulnerability in Squid-cache Squid with a CVSS 3.x base score of 7.5. 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-295.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 3% (85th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-295
Affected product: Squid-cache Squid
Published: 2021-10-18
Last modified: 2026-06-17

Description

An issue was discovered in Squid 5.0.6 through 5.1.x before 5.2. When validating an origin server or peer certificate, Squid may incorrectly classify certain certificates as trusted. This problem allows a remote server to obtain security trust well improperly. This indication of trust may be passed along to clients, allowing access to unsafe or hijacked services.

Frequently asked questions

What is CVE-2021-41611?: An issue was discovered in Squid 5.0.6 through 5.1.x before 5.2. When validating an origin server or peer certificate, Squid may incorrectly classify certain certificates as trusted. This problem allows a remote server to obtain security trust well improperly. This indication of trust may be passed along to clients, allowing access to unsafe or hijacked services.
How severe is CVE-2021-41611?: CVE-2021-41611 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-41611 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-41611?: CVE-2021-41611 primarily affects Squid-cache Squid. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-41611?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-41611 published?: CVE-2021-41611 was published on 2021-10-18 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*

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