THREATPORT/VULNERABILITY/CVE-2019-12521
MEDIUM SEVERITY

CVE-2019-12521

Squid vulnerability

CVSS
5.9
EPSS
5.8%
EPSS pct
92th
Exploited
No known
An issue was discovered in Squid through 4.7. When Squid is parsing ESI, it keeps the ESI elements in ESIContext. ESIContext contains a buffer for holding a stack of ESIElements. When a new ESIElement is parsed, it is added via addStackElement. addStackElement has a check for the number of elements in this buffer, but it's off by 1, leading to a Heap Overflow of 1 element. The overflow is within the same structure so it can't affect adjacent memory blocks, and thus just leads to a crash while processing.
Affected vendor
Squid Cache
Affected product
Squid
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness type (CWE)
Published
2020-04-15

Risk analysis

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

Its EPSS score of 5.8% reflects a lower probability of exploitation activity in the wild over the next 30 days, placing it above 92% of all scored CVEs.

Check your external exposure to CVE-2019-12521

  • Confirm whether Squid Cache Squid is running on any internet-facing host or subdomain.
  • Match discovered service fingerprints against the version affected by CVE-2019-12521.
  • Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2019-12521

ThreatPort's external attack surface scanner checks your internet-facing assets — agentlessly, from the outside in — for the exposed services and versions that CVE-2019-12521 affects, then prioritises the finding by real risk using CISA KEV and FIRST.org EPSS.

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Are you exposed to CVE-2019-12521?

Run an instant, non-intrusive external scan to check your attack surface for CVE-2019-12521.

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