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 its off by 1, leading to a Heap Overflow of 1 element. The overflow is within the same structure so it cant affect adjacent memory blocks, and thus just leads to a crash while processing.
Weakness
A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Squid | Squid-cache | 3.0 (including) | 3.5.28 (including) |
| Squid | Squid-cache | 4.0 (including) | 4.7 (including) |
| Squid | Squid-cache | 5.0 (including) | 5.0.1 (including) |
| Red Hat Enterprise Linux 8 | RedHat | squid:4-8030020200828070549.30b713e6 | * |
| Squid | Ubuntu | devel | * |
| Squid | Ubuntu | eoan | * |
| Squid | Ubuntu | esm-infra/focal | * |
| Squid | Ubuntu | focal | * |
| Squid | Ubuntu | groovy | * |
| Squid | Ubuntu | hirsute | * |
| Squid | Ubuntu | trusty | * |
| Squid | Ubuntu | upstream | * |
| Squid3 | Ubuntu | bionic | * |
| Squid3 | Ubuntu | esm-infra/bionic | * |
| Squid3 | Ubuntu | esm-infra/xenial | * |
| Squid3 | Ubuntu | precise/esm | * |
| Squid3 | Ubuntu | trusty | * |
| Squid3 | Ubuntu | xenial | * |
Potential Mitigations
References
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00018.html
- http://www.openwall.com/lists/oss-security/2020/04/23/1
- https://gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12521.txt
- https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html
- https://security.gentoo.org/glsa/202005-05
- https://security.netapp.com/advisory/ntap-20210205-0006/
- https://usn.ubuntu.com/4356-1/
- https://www.debian.org/security/2020/dsa-4682
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00018.html
- http://www.openwall.com/lists/oss-security/2020/04/23/1
- https://gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12521.txt
- https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html
- https://security.gentoo.org/glsa/202005-05
- https://security.netapp.com/advisory/ntap-20210205-0006/
- https://usn.ubuntu.com/4356-1/
- https://www.debian.org/security/2020/dsa-4682