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Fencer Vulns
low 3.7

CVE-2021-28116 json

Squid through 4.14 and 5.x through 5.0.5, in some configurations, allows information disclosure because of an out-of-bounds read in WCCP pr…

published 2021-03-09 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-14817

cvss
3.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
12.9%
EPSS 12.9% chance of exploitation in 30 days, percentile 96%
public exploits
0
none known

Summary

Squid through 4.14 and 5.x through 5.0.5, in some configurations, allows information disclosure because of an out-of-bounds read in WCCP protocol data. This can be leveraged as part of a chain for remote code execution as nobody.

Patch / fix

  • squid Debian 14, Debian 13, Debian 12 5.2-1

debian advisories DEBIAN-CVE-2021-28116

  • squid Ubuntu 20.04 LTS 4.10-1ubuntu1.5
  • squid Ubuntu 22.04 LTS 4.13-10ubuntu5
  • squid3 Ubuntu 18.04 LTS 3.5.27-1ubuntu1.12

ubuntu advisories UBUNTU-CVE-2021-28116

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • squid RHEL 8 7:4.15-3.module+el8.6.0+14176+9782b8ab
  • libecap RHEL 8 1.0.1-2.module+el8.1.0+4044+36416a77

red hat advisories RHSA-2022:1939

  • squid SLE Module for Server Applications 15 SP3, SLE Module for Server Applications 15 SP2 4.17-5.29.1
  • squid SLES for SAP 12 SP5, SLES 12 SP5 4.17-4.21.1

suse advisories SUSE-SU-2021:3485-1SUSE-SU-2021:3334-1

  • squid openSUSE Tumbleweed 5.2-1.1
  • squid openSUSE Leap 15.2 4.17-lp152.2.12.1
  • squid openSUSE Leap 15.3 4.17-5.29.1

opensuse advisories openSUSE-SU-2024:11559-1openSUSE-SU-2021:1419-1openSUSE-SU-2021:3485-1

  • squid AlmaLinux 8 7:4.15-3.module_el8.6.0+2741+01592ae8
  • libecap AlmaLinux 8 1.0.1-2.module_el8.6.0+2741+01592ae8

almalinux advisories ALSA-2022:1939

  • squid Rocky Linux 8 7:4.15-3.module+el8.6.0+1044+67ab5d0a.2
  • libecap Rocky Linux 8 1.0.1-2.module+el8.4.0+404+316a0dc5

rocky linux advisories RLSA-2022:1939

  • squid Alpine 3.12, Alpine 3.11 4.17-r0
  • squid Alpine 3.14, Alpine 3.13 5.0.6-r1
  • squid Alpine 3.24, Alpine 3.23, Alpine 3.22 +7 more 5.2-r0

alpine advisories ALPINE-CVE-2021-28116

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • squid Arch Linux 5.2-1

arch linux advisories AVG-1667

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-28116 updated cvss 5.3

squid: out-of-bounds read in WCCP protocol data may lead to information disclosure

  • Red Hat Enterprise Linux 6 squid, squid34 Red Hat Enterprise Linux 7 squid, squid-sysvinit, squid-migration-script
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) squid 4.15-3.module+el8.6.0+14176+9782b8ab, libecap 1.0.1-2.module+el8.1.0+4044+36416a77
    fixed: vendor fix RHSA-2022:1939
  • Red Hat Enterprise Linux 9 squid
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

12.95% chance of exploitation in the next 30 days, higher than 96% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 3.7 CVSS:3.1/AC:H/AV:N/A:N/C:L/I:N/PR:N/S:U/UI:N
CNA 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:P/I:N/A:N

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.