How severe is CVE-2016-3948?

CVE-2016-3948 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 none, integrity none, and availability high.

Is CVE-2016-3948 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 35% (98th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2016-3948?

CVE-2016-3948 primarily affects Squid-cache Squid. In total, 158 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2016-3948?

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-2016-3948 published?

CVE-2016-3948 was published on 2016-04-07 and last updated on 2026-06-17.

CVE-2016-3948

CVE-2016-3948 is a high-severity vulnerability in Squid-cache Squid with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 35% places it in the 98th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-119.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 35% (98th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-119
Affected product: Squid-cache Squid
Published: 2016-04-07
Last modified: 2026-06-17

Description

Squid 3.x before 3.5.16 and 4.x before 4.0.8 improperly perform bounds checking, which allows remote attackers to cause a denial of service via a crafted HTTP response, related to Vary headers.

Frequently asked questions

What is CVE-2016-3948?: Squid 3.x before 3.5.16 and 4.x before 4.0.8 improperly perform bounds checking, which allows remote attackers to cause a denial of service via a crafted HTTP response, related to Vary headers.
How severe is CVE-2016-3948?: CVE-2016-3948 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 none, integrity none, and availability high.
Is CVE-2016-3948 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 35% (98th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2016-3948?: CVE-2016-3948 primarily affects Squid-cache Squid. In total, 158 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2016-3948?: 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-2016-3948 published?: CVE-2016-3948 was published on 2016-04-07 and last updated on 2026-06-17.

References

Affected products (158)

cpe:2.3:a:squid-cache:squid:3.0:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0:-:pre1:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0:-:pre2:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0:-:pre3:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0:-:pre4:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0:-:pre5:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0:-:pre6:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0:-:pre7:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0:rc4:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable1:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable2:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable3:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable4:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable5:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable6:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable7:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable8:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable9:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable10:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable11:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable11:rc1:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable12:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable13:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable14:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable15:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable16:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable16:rc1:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable17:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable18:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable19:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable20:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable21:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable22:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable23:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable24:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.0.stable25:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.1:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.1.0.1:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.1.0.2:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:3.1.0.3:*:*:*:*:*:*:*

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Threat intelligence

Threat-intel indicators referencing this CVE:

200.89.159.59 (ipv4-addr)