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.
Published 2020-04-15 19:15:12
Updated 2021-07-21 11:39:24
Source MITRE
View at NVD,   CVE.org
Vulnerability category: Memory Corruption

Threat overview for CVE-2019-12521

Top countries where our scanners detected CVE-2019-12521
Top open port discovered on systems with this issue 3128
IPs affected by CVE-2019-12521 2,253,195
Threat actors abusing to this issue? Yes
Find out if you* are affected by CVE-2019-12521!
*Directly or indirectly through your vendors, service providers and 3rd parties. Powered by attack surface intelligence from SecurityScorecard.

Exploit prediction scoring system (EPSS) score for CVE-2019-12521

Probability of exploitation activity in the next 30 days: 2.14%

Percentile, the proportion of vulnerabilities that are scored at or less: ~ 89 % EPSS Score History EPSS FAQ

CVSS scores for CVE-2019-12521

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source
4.3
MEDIUM AV:N/AC:M/Au:N/C:N/I:N/A:P
8.6
2.9
NIST
5.9
MEDIUM CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
2.2
3.6
NIST

CWE ids for CVE-2019-12521

  • A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.
    Assigned by: nvd@nist.gov (Primary)
  • The product writes data past the end, or before the beginning, of the intended buffer.
    Assigned by: nvd@nist.gov (Primary)

References for CVE-2019-12521

Products affected by CVE-2019-12521

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