CVE-2019-12521: canonical ubuntu_linux Off-by-one Error
Vulnerability summary
CVE-2019-12521 is a medium (CVSS 5.9) Off-by-one Error vulnerability in canonical ubuntu_linux. EPSS estimates a 5.91% chance of exploitation in the next 30 days, higher than 93.1% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 9 · Related 6Timeline
- 15-04-2020PublishedVulnerability first disclosed.
- 04-08-2024Last modifiedVulnerability information updated.
Description
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.
CVSS metrics
5 scores · 4 sources · 2 versions- OSV · AlpineEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
5.91%
Chance of exploitation in the next 30 days
Percentile
93%
Versus all other CVEs
30-day change
0.00 pp
From 5.91% on 18-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Debian2 products
- squid< 4.11-1
- debian_linuxEOL9.0 | 10.0
Ubuntu2 products
- squid< 4.10-1ubuntu1.1
- squid3< 3.5.12-1ubuntu7.11 | < 3.5.27-1ubuntu1.6
Alpine1 product
- squid≥ 3.0, < 4.11-r0
Canonical1 product
- ubuntu_linuxEOL16.04 | 18.04 | 19.10 | 20.04
Opensuse1 product
- leapEOL15.1
Squid-cache1 product
- squid≥ 3.0, ≤ 3.5.28 | ≥ 4.0, ≤ 4.7 | ≥ 5.0, ≤ 5.0.1
6 vendors · 8 products
References
14 links- gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12521.txtX Refsource MISCThird Party AdvisoryREPORT
- www.openwall.com/lists/oss-security/2020/04/23/1Mailing ListX Refsource MLISTPatchThird Party Advisory
- lists.opensuse.org/opensuse-security-announce/2020-05/msg00018.htmlVendor AdvisoryX Refsource SUSEMailing ListThird Party Advisory
- lists.debian.org/debian-lts-announce/2020/07/msg00009.htmlMailing ListX Refsource MLISTThird Party Advisory