How severe is CVE-2019-18677?

CVE-2019-18677 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2019-18677 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 7% (94th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-18677?

CVE-2019-18677 primarily affects Squid-cache Squid. In total, 15 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-18677?

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

When was CVE-2019-18677 published?

CVE-2019-18677 was published on 2019-11-26 and last updated on 2026-06-17.

CVE-2019-18677

CVE-2019-18677 is a medium-severity vulnerability in Squid-cache Squid with a CVSS 3.x base score of 6.1. 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-352.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v2: 5.8
EPSS exploit prediction: 7% (94th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-352
Affected product: Squid-cache Squid
Published: 2019-11-26
Last modified: 2026-06-17

Description

An issue was discovered in Squid 3.x and 4.x through 4.8 when the append_domain setting is used (because the appended characters do not properly interact with hostname length restrictions). Due to incorrect message processing, it can inappropriately redirect traffic to origins it should not be delivered to.

Frequently asked questions

What is CVE-2019-18677?: An issue was discovered in Squid 3.x and 4.x through 4.8 when the append_domain setting is used (because the appended characters do not properly interact with hostname length restrictions). Due to incorrect message processing, it can inappropriately redirect traffic to origins it should not be delivered to.
How severe is CVE-2019-18677?: CVE-2019-18677 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2019-18677 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 7% (94th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-18677?: CVE-2019-18677 primarily affects Squid-cache Squid. In total, 15 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-18677?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2019-18677 published?: CVE-2019-18677 was published on 2019-11-26 and last updated on 2026-06-17.

References

Affected products (15)

cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:2.7:stable2:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:2.7:stable3:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:2.7:stable4:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:2.7:stable5:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:2.7:stable6:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:2.7:stable7:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:2.7:stable8:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:2.7:stable9:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:19.04:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:19.10:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:30:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*

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Threat intelligence

Threat-intel indicators referencing this CVE:

200.89.159.59 (ipv4-addr)
192.3.127.40 (ipv4-addr)