CVE-2019-12521

mediumpriority · track · 26EPSS 0.059 · 93 %ileEURUUS
grimoire priorityP3 · Track
Exploitable?
—
no known exploitation
Likely / severe?
5.91% (93rd) EPSS
CVSS 4.3 · medium
Is it mine?
26 products
Check your exposure
Who says so?
4 sources
cnnvd · enisa_euvd · fstec_bdu · nvd

EPSS · scored 2026-10-27

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.

01

cvss

Technical severity, 0–10. One row per scoring source.

5.9
010

base score 0–10 · higher = more severe · hover a vector to decode

v2.04.3mediumAV:N/AC:M/Au:N/C:N/I:N/A:Pprimary · NVD / NIST USexploitability 8.6 · impact 2.9
v3.15.9mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:Hprimary · NVD / NIST USexploitability 2.2 · impact 3.6
v3.15.9mediumAV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:Hsecondary · FSTEC (BDU) RU
v3.15.4mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:Usecondary · CVSS-BT (t0sche)
02

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-193USprimaryCWE-787USprimaryCWE-787US
03

affected products (26)

Products and version ranges known to be affected.

showing 20 of 26
04

also known as (4)

Other names and identifiers for this entity.

05

sources

Which sources assert this record, and when.

cnnvdenisa_euvdfstec_bdunvdNVDCVE.orgMITRE
published 2020-04-15modified 2026-06-17
07

references (40)

External citations — patches, advisories, analysis.

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