CVE-2019-12521
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.
Does this matter?
Lower severity and a low EPSS score (5.91%). Track it; it rarely justifies an emergency change on its own.
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 3.1
- 5.9 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 5.91% probability · 93th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-193, CWE-787
- Affected
- squid-cache/squid · canonical/ubuntu linux · debian/debian linux · opensuse/leap
- Source
- cve@mitre.org
EPSS 5.9% since 27 October 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00018.htmlMailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2020/04/23/1Mailing List, Patch, Third Party Advisory
- https://gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12521.txtThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2020/07/msg00009.htmlMailing List, Third Party Advisory
- https://security.gentoo.org/glsa/202005-05Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210205-0006/Third Party Advisory
- https://usn.ubuntu.com/4356-1/Third Party Advisory
- https://www.debian.org/security/2020/dsa-4682Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00018.htmlMailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2020/04/23/1Mailing List, Patch, Third Party Advisory
- https://gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12521.txtThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2020/07/msg00009.htmlMailing List, Third Party Advisory
- https://security.gentoo.org/glsa/202005-05Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210205-0006/Third Party Advisory
- https://usn.ubuntu.com/4356-1/Third Party Advisory
- https://www.debian.org/security/2020/dsa-4682Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.