THREATPORT/VULNERABILITY/CVE-2020-15811
MEDIUM SEVERITY

CVE-2020-15811

Squid vulnerability

CVSS
6.5
EPSS
4.2%
EPSS pct
90th
Exploited
No known
An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Splitting attacks may succeed against HTTP and HTTPS traffic. This leads to cache poisoning. This allows any client, including browser scripts, to bypass local security and poison the browser cache and any downstream caches with content from an arbitrary source. Squid uses a string search instead of parsing the Transfer-Encoding header to find chunked encoding. This allows an attacker to hide a second request inside Transfer-Encoding: it is interpreted by Squid as chunked and split out into a second request delivered upstream. Squid will then deliver two distinct responses to the client, corrupting any downstream caches.
Affected vendor
Squid Cache
Affected product
Squid
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Weakness type (CWE)
Published
2020-09-02

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, low attack complexity, requiring low privileges, no user interaction. Successful exploitation leads to high impact to integrity.

Its EPSS score of 4.2% reflects a lower probability of exploitation activity in the wild over the next 30 days, placing it above 90% of all scored CVEs.

Check your external exposure to CVE-2020-15811

  • Confirm whether Squid Cache Squid is running on any internet-facing host or subdomain.
  • Match discovered service fingerprints against the version affected by CVE-2020-15811.
  • Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2020-15811

ThreatPort's external attack surface scanner checks your internet-facing assets — agentlessly, from the outside in — for the exposed services and versions that CVE-2020-15811 affects, then prioritises the finding by real risk using CISA KEV and FIRST.org EPSS.

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Are you exposed to CVE-2020-15811?

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