How severe is CVE-2020-15049?

CVE-2020-15049 has a CVSS 3.x base score of 9.9, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2020-15049 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 6% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-15049?

CVE-2020-15049 primarily affects Squid-cache Squid. In total, 11 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-15049?

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

When was CVE-2020-15049 published?

CVE-2020-15049 was published on 2020-06-30 and last updated on 2026-06-17.

CVE-2020-15049

CVE-2020-15049 is a critical-severity vulnerability in Squid-cache Squid with a CVSS 3.x base score of 9.9. 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-444.

Key facts

Severity: Critical (CVSS 3.x base score 9.9)
CVSS v2: 6.5
EPSS exploit prediction: 6% (92nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-444
Affected product: Squid-cache Squid
Published: 2020-06-30
Last modified: 2026-06-17

Description

An issue was discovered in http/ContentLengthInterpreter.cc in Squid before 4.12 and 5.x before 5.0.3. A Request Smuggling and Poisoning attack can succeed against the HTTP cache. The client sends an HTTP request with a Content-Length header containing "+\ "-" or an uncommon shell whitespace character prefix to the length field-value.

Frequently asked questions

What is CVE-2020-15049?: An issue was discovered in http/ContentLengthInterpreter.cc in Squid before 4.12 and 5.x before 5.0.3. A Request Smuggling and Poisoning attack can succeed against the HTTP cache. The client sends an HTTP request with a Content-Length header containing "+\ "-" or an uncommon shell whitespace character prefix to the length field-value.
How severe is CVE-2020-15049?: CVE-2020-15049 has a CVSS 3.x base score of 9.9, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-15049 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 6% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-15049?: CVE-2020-15049 primarily affects Squid-cache Squid. In total, 11 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-15049?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2020-15049 published?: CVE-2020-15049 was published on 2020-06-30 and last updated on 2026-06-17.

References

Affected products (11)

cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:*
cpe:2.3:a:squid-cache:squid:2.7:*:*:*:*:*:*:*
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:fedoraproject:fedora:31:*:*:*:*:*:*:*

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Browse all CWE-444 (HTTP Request/Response Smuggling) vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE:

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