CVE-2019-12521
MEDIUMEPSS 92th pctlDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Exploit Intelligence
High risk: more likely to be exploited than 92% of all known CVEs.
References
Related Vulnerabilities
Other CWE-193 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2021-3156 | High | 7.8 | 99% | KEV | Fix |
| CVE-2003-0466 | Critical | 9.8 | 78% | - | - |
| CVE-2023-44444 | High | 7.8 | 56% | - | Fix |
| CVE-2021-23017 | High | 7.7 | 53% | - | Fix |
| CVE-2023-28709 | High | 7.5 | 50% | - | Fix |
| CVE-2018-8828 | Critical | 9.8 | 31% | - | Fix |
Common questions
How do I fix CVE-2019-12521?
Published advisories record a fix for 3 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2019-12521 being actively exploited?
Not that we know of. CVE-2019-12521 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 5.8% is the estimated probability that it will be exploited in the next 30 days. That is higher than 92% of all scored CVEs.
How severe is CVE-2019-12521?
CVE-2019-12521 has a CVSS v3 base score of 5.9, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2019-12521 affect?
Published advisories record a fix for squid (Debian), squid (Ubuntu), squid3 (Ubuntu). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.