UBUNTU-CVE-2019-12521

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    UBUNTU-CVE-2019-12521

    Published: 15 Apr 2020Last Modified: 4 Feb 2026
    Upstream:
    CVE-2019-12521
    Aliases:
    USN-4356-1

    Summary:

    Details: 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.

    References: https://ubuntu.com/security/CVE-2019-12521, https://gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12521.txt, http://www.squid-cache.org/Advisories/SQUID-2019_12.txt, https://ubuntu.com/security/notices/USN-4356-1, https://www.cve.org/CVERecord?id=CVE-2019-12521

    Affected packages

    Package

    Name: squid3

    Purl: pkg:deb/ubuntu/[email protected]?arch=source&distro=xenial

    Affected ranges

    Type: ECOSYSTEM

    Events:

    Introduced- 0
    Fixed -3.5.12-1ubuntu7.11

    Affected versions

    3.3.8-1ubuntu16
    3.3.8-1ubuntu17

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    UBUNTU-CVE-2019-12521 | CVE-DB