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Fencer Vulns
high 7.5

CVE-2026-33526 json

Squid vulnerable to Denial of Service in ICP Request handling

published 2026-03-26 7 mo ago modified 2026-07-15 3 mo ago also EUVD-2026-16068

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
9.1%
EPSS 9.1% chance of exploitation in 30 days, percentile 95%
public exploits
0
none known

Summary

Squid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero `icp_port`). This problem _cannot_ be mitigated by denying ICP queries using `icp_access` rules. Version 7.5 contains a patch.

Patch / fix

  • Red Hat Red Hat Enterprise Linux 10 7:6.10-6.el10_1.3
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support 7:6.10-5.el10_0.2
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support 7:3.5.20-17.el7_9.16
  • Red Hat Red Hat Enterprise Linux 8 8100020260408092701.489197e6
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 8040020260514123440.522a0ee4
  • Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 8040020260514123440.522a0ee4
  • Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support 8060020260518090356.ad008a3a
  • Red Hat Red Hat Enterprise Linux 8.6 Telecommunications Update Service 8060020260518090356.ad008a3a
  • Red Hat Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions 8060020260518090356.ad008a3a
  • Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service 8080020260514105733.63b34585
  • Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 8080020260514105733.63b34585
  • Red Hat Red Hat Enterprise Linux 9 7:5.5-22.el9_7.4
  • Red Hat Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions 7:5.2-1.el9_0.10
  • Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 7:5.5-5.el9_2.11
  • Red Hat Red Hat Enterprise Linux 9.4 Extended Update Support 7:5.5-13.el9_4.5
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support 7:5.5-19.el9_6.3
  • squid Debian 12 5.7-2+deb12u6
  • squid Debian 13 6.13-2+deb13u2
  • squid Debian 14 7.5-1

debian advisories DEBIAN-CVE-2026-33526

  • squid Ubuntu 22.04 LTS 5.9-0ubuntu0.22.04.5
  • squid Ubuntu 24.04 LTS 6.14-0ubuntu0.24.04.2
  • squid Ubuntu 25.10 6.14-0ubuntu0.25.10.2
  • squid Ubuntu Pro 20.04 LTS 4.10-1ubuntu1.13+esm3
  • squid3 Ubuntu Pro 16.04 LTS 3.5.12-1ubuntu7.16+esm7
  • squid3 Ubuntu Pro 18.04 LTS 3.5.27-1ubuntu1.14+esm6

ubuntu advisories UBUNTU-CVE-2026-33526

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 7:4.15-10.module+el8.10.0+24189+04a20c8a.11
  • libecap RHEL 8 1.0.1-2.module+el8.9.0+19703+a1da7223
  • squid RHEL 10.1 7:6.10-6.el10_1.3
  • squid RHEL 9 7:5.5-22.el9_7.4
  • squid RHEL 8.8 TUS, RHEL 8.8 E4S 7:4.15-6.module+el8.8.0+24284+6402ee68.10
  • libecap RHEL 8.8 TUS, RHEL 8.8 E4S, RHEL 8.6 TUS +4 more 1.0.1-2.module+el8.1.0+4044+36416a77
  • squid RHEL 8.4 EUS_LONG_LIFE, RHEL 8.4 AUS 7:4.11-4.module+el8.4.0+24287+ae9ea41b.11
  • squid RHEL 8.6 TUS, RHEL 8.6 E4S, RHEL 8.6 AUS 7:4.15-3.module+el8.6.0+24307+cba8e5bb.9

red hat advisories RHSA-2026:20580RHSA-2026:20564RHSA-2026:20565RHSA-2026:11901RHSA-2026:10257RHSA-2026:10255

  • squid SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +5 more 5.7-150400.3.41.1
  • squid SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Server Applications 15 SP7 6.14-150600.3.20.1
  • squid SLES for SAP applications 16.0, SLES 16.0 6.14-160000.1.1

suse advisories SUSE-SU-2026:4909-1SUSE-SU-2026:4621-1SUSE-SU-2026:24224-1

  • squid openSUSE Leap 16.0 6.14-160000.1.1

opensuse advisories openSUSE-SU-2026:22080-1

  • squid AlmaLinux 8 7:4.15-10.module_el8.10.0+4163+e77fcdac.11
  • libecap AlmaLinux 8 1.0.1-2.module_el8.6.0+2741+01592ae8
  • libecap AlmaLinux 8 1.0.1-2.module_el8.6.0+3048+383bc947
  • squid AlmaLinux 10 7:6.10-6.el10_1.3
  • squid AlmaLinux 9 7:5.5-22.el9_7.4

almalinux advisories ALSA-2026:8317ALSA-2026:8119ALSA-2026:6301

  • squid Rocky Linux 8 7:4.15-10.module+el8.10.0+1928+e8441768.5
  • squid Rocky Linux 8 7:4.15-10.module+el8.10.0+1985+eaf982f0.6
  • squid Rocky Linux 8 7:4.15-10.module+el8.10.0+1885+e30b7122.3
  • squid Rocky Linux 8 7:4.15-10.module+el8.10.0+2080+49064dbd.9
  • squid Rocky Linux 8 7:4.15-10.module+el8.10.0+1758+80ba9f4b
  • squid Rocky Linux 8 7:4.15-10.module+el8.10.0+1881+7e31fb44.1
  • libecap Rocky Linux 8 1.0.1-2.module+el8.9.0+1437+df5ea8f0
  • squid Rocky Linux 10 7:6.10-6.el10_1.3

rocky linux advisories RLSA-2026:8317RLSA-2026:8119RLSA-2026:6301

  • squid Azure Linux 3.0 6.13-4

azure linux advisories AZL-80762

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-33526 updated cvss 7.5

squid: Squid: Denial of Service via heap Use-After-Free vulnerability in ICP handling

  • Red Hat Enterprise Linux 6 squid, squid34
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) libecap 1.0.1-2.module+el8.9.0+19703+a1da7223, squid 4.15-10.module+el8.10.0+24189+04a20c8a.11
    fixed: vendor fix RHSA-2026:8317
  • Red Hat Enterprise Linux AppStream (v. 9) squid 5.5-22.el9_7.4
    fixed: vendor fix RHSA-2026:6301
  • Red Hat Enterprise Linux AppStream (v. 10) squid 6.10-6.el10_1.3
    fixed: vendor fix RHSA-2026:8119
  • Red Hat Enterprise Linux AppStream AUS (v.8.4) libecap 1.0.1-2.module+el8.1.0+4044+36416a77, squid 4.11-4.module+el8.4.0+24287+ae9ea41b.11
    fixed: vendor fix RHSA-2026:20564
  • Red Hat Enterprise Linux AppStream AUS (v.8.6) libecap 1.0.1-2.module+el8.1.0+4044+36416a77, squid 4.15-3.module+el8.6.0+24307+cba8e5bb.9 Red Hat Enterprise Linux AppStream E4S (v.8.6) libecap 1.0.1-2.module+el8.1.0+4044+36416a77, squid 4.15-3.module+el8.6.0+24307+cba8e5bb.9
    fixed: vendor fix RHSA-2026:20565
  • Red Hat Enterprise Linux AppStream E4S (v.8.8) libecap 1.0.1-2.module+el8.1.0+4044+36416a77, squid 4.15-6.module+el8.8.0+24284+6402ee68.10
    fixed: vendor fix RHSA-2026:20580
  • Red Hat Enterprise Linux AppStream E4S (v.9.0) squid 5.2-1.el9_0.10
    fixed: vendor fix RHSA-2026:10256
show 9 more
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) squid 5.5-5.el9_2.11
    fixed: vendor fix RHSA-2026:10257
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) squid 6.10-5.el10_0.2
    fixed: vendor fix RHSA-2026:11901
  • Red Hat Enterprise Linux AppStream EUS (v.9.4) squid 5.5-13.el9_4.5
    fixed: vendor fix RHSA-2026:10255
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) squid 5.5-19.el9_6.3
    fixed: vendor fix RHSA-2026:9220
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) libecap 1.0.1-2.module+el8.1.0+4044+36416a77, squid 4.11-4.module+el8.4.0+24287+ae9ea41b.11
    fixed: vendor fix RHSA-2026:20564
  • Red Hat Enterprise Linux AppStream TUS (v.8.6) libecap 1.0.1-2.module+el8.1.0+4044+36416a77, squid 4.15-3.module+el8.6.0+24307+cba8e5bb.9
    fixed: vendor fix RHSA-2026:20565
  • Red Hat Enterprise Linux AppStream TUS (v.8.8) libecap 1.0.1-2.module+el8.1.0+4044+36416a77, squid 4.15-6.module+el8.8.0+24284+6402ee68.10
    fixed: vendor fix RHSA-2026:20580
  • Red Hat Enterprise Linux Server (v. 7 ELS) squid 3.5.20-17.el7_9.16
    fixed: vendor fix RHSA-2026:8880
  • Red Hat Enterprise Linux Server (v. 7 ELS) squid-migration-script 3.5.20-17.el7_9.16 Red Hat Enterprise Linux Server Optional (v. 7 ELS) squid-sysvinit 3.5.20-17.el7_9.16
    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

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

9.08% chance of exploitation in the next 30 days, higher than 95% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 9.2 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 4.0 9.2 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • squid-cache squid
  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
  • Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On
  • Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  • Red Hat Red Hat Enterprise Linux 8.6 Telecommunications Update Service
  • Red Hat Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service
  • Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9.4 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 6

Classification

Weakness
  • CWE-416 Use After Free
  • CWE-826 Premature Release of Resource During Expected Lifetime
  • CWE-825 Expired Pointer Dereference

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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.