Description
Squid is a caching proxy for the Web. Due to an Improper Validation of Specified Index bug, Squid versions 3.3.0.1 through 5.9 and 6.0 prior to 6.4 compiled using `--with-openssl` are vulnerable to a Denial of Service attack against SSL Certificate validation. This problem allows a remote server to perform Denial of Service against Squid Proxy by initiating a TLS Handshake with a specially crafted SSL Certificate in a server certificate chain. This attack is limited to HTTPS and SSL-Bump. This bug is fixed in Squid version 6.4. In addition, patches addressing this problem for the stable releases can be found in Squid's patch archives. Those who you use a prepackaged version of Squid should refer to the package vendor for availability information on updated packages.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| squid-cache | squid | >= 3.3.0.1, < 6.4 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | squid | 6.5-1 | — |
| Debian 13 | squid | 6.5-1 | — |
| Debian 12 | squid | 5.7-2+deb12u1 | DSA-5637-1 |
| Debian 11 | squid | 4.13-10+deb11u3 | DSA-5637-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 24.04 LTS | squid | 6.1-2ubuntu2 | — |
| Ubuntu 22.04 LTS | squid | 5.7-0ubuntu0.22.04.2 | USN-6500-1 |
| Ubuntu 20.04 LTS | squid | 4.10-1ubuntu1.8 | USN-6500-1 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 18.04 LTS | squid3 | No fix yet | — |
| Ubuntu Pro 16.04 LTS | squid3 | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9 | squid | 7:5.5-6.el9_3.5 | RHSA-2024:0071 |
| RHEL 8 | libecap +1 | 1.0.1-2.module+el8.9.0+19703+a1da7223 | RHSA-2024:0046 |
| RHEL 8 | squid | 7:4.15-7.module+el8.9.0+20975+25f17541.5 | RHSA-2024:0046 |
| RHEL 7 | squid +2 | 7:3.5.20-17.el7_9.10 | RHSA-2024:1787 |
Show 10 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9.2 EUS | squid | 7:5.5-5.el9_2.3 | RHSA-2024:0072 |
| RHEL 9.0 EUS | squid | 7:5.2-1.el9_0.4 | RHSA-2024:1153 |
| RHEL 8.8 EUS | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2024:0397 |
| RHEL 8.8 EUS | squid | 7:4.15-6.module+el8.8.0+21068+0ecbc070.3 | RHSA-2024:0397 |
| RHEL 8.6 EUS | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2024:0771 |
| RHEL 8.6 EUS | squid | 7:4.15-3.module+el8.6.0+21069+a1561e3d.4 | RHSA-2024:0771 |
| RHEL 8.4 TUS | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2024:0773 |
| RHEL 8.4 TUS | squid | 7:4.11-4.module+el8.4.0+21174+3894a031.6 | RHSA-2024:0773 |
| RHEL 8.4 E4S | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2024:0773 |
| RHEL 8.4 E4S | squid | 7:4.11-4.module+el8.4.0+21174+3894a031.6 | RHSA-2024:0773 |
| RHEL 8.4 AUS | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2024:0773 |
| RHEL 8.4 AUS | squid | 7:4.11-4.module+el8.4.0+21174+3894a031.6 | RHSA-2024:0773 |
| RHEL 8.2 TUS | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2024:0772 |
| RHEL 8.2 TUS | squid | 7:4.4-8.module+el8.2.0+21173+22259b09.7 | RHSA-2024:0772 |
| RHEL 8.2 E4S | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2024:0772 |
| RHEL 8.2 E4S | squid | 7:4.4-8.module+el8.2.0+21173+22259b09.7 | RHSA-2024:0772 |
| RHEL 8.2 AUS | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2024:0772 |
| RHEL 8.2 AUS | squid | 7:4.4-8.module+el8.2.0+21173+22259b09.7 | RHSA-2024:0772 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 9 | squid | 7:5.5-6.el9_3.5 | ALSA-2024:0071 |
| AlmaLinux 8 | libecap +1 | 1.0.1-2.module_el8.6.0+2741+01592ae8 | ALSA-2024:0046 |
| AlmaLinux 8 | squid | 7:4.15-7.module_el8.9.0+3708+6acaac63.5 | ALSA-2024:0046 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | libecap | 1.0.1-2.module+el8.9.0+1437+df5ea8f0 | RLSA-2024:0046 |
| Rocky Linux 8 | squid | 7:4.15-7.module+el8.9.0+1568+6d4fd5d4.1 | RLSA-2024:0046 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP5 | squid | 5.7-150400.3.12.1 | SUSE-SU-2023:4380-1 |
| SLES 15 SP4 | squid | 5.7-150400.3.12.1 | SUSE-SU-2023:4380-1 |
| SLES 15 SP3 | squid | 4.17-150000.5.38.1 | SUSE-SU-2023:4384-1 |
| SLES 15 SP2 | squid | 4.17-150000.5.38.1 | SUSE-SU-2023:4384-1 |
| SLES 15 SP1 | squid | 4.17-150000.5.38.1 | SUSE-SU-2023:4384-1 |
Show 9 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP5 | squid | 4.17-4.30.1 | SUSE-SU-2023:4381-1 |
| SLES for SAP 15 SP3 | squid | 4.17-150000.5.38.1 | SUSE-SU-2023:4384-1 |
| SLES for SAP 15 SP2 | squid | 4.17-150000.5.38.1 | SUSE-SU-2023:4384-1 |
| SLES for SAP 15 SP1 | squid | 4.17-150000.5.38.1 | SUSE-SU-2023:4384-1 |
| SLES for SAP 12 SP5 | squid | 4.17-4.30.1 | SUSE-SU-2023:4381-1 |
| SLE HPC 15 SP3 | squid | 4.17-150000.5.38.1 | SUSE-SU-2023:4384-1 |
| SLE HPC 15 SP2 | squid | 4.17-150000.5.38.1 | SUSE-SU-2023:4384-1 |
| SLE HPC 15 SP1 | squid | 4.17-150000.5.38.1 | SUSE-SU-2023:4384-1 |
| SUSE Enterprise Storage 7.1 | squid | 4.17-150000.5.38.1 | SUSE-SU-2023:4384-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | squid | 6.4-1.1 | openSUSE-SU-2024:13398-1 |
| openSUSE Leap 15.5 | squid | 5.7-150400.3.12.1 | SUSE-SU-2023:4380-1 |
| openSUSE Leap 15.4 | squid | 5.7-150400.3.12.1 | SUSE-SU-2023:4380-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | squid | 6.4-r0 | — |
| Alpine v3.23 | squid | 6.4-r0 | — |
| Alpine v3.22 | squid | 6.4-r0 | — |
| Alpine v3.21 | squid | 6.4-r0 | — |
| Alpine v3.20 | squid | 6.4-r0 | — |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | squid | 6.4-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | squid | 7:5.8-1.amzn2023.0.2 | ALAS2023-2023-429 |
| Amazon Linux 2 | squid +2 | 7:3.5.20-17.amzn2.7.14 | ALAS2-2023-2354 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 2 (CBL-Mariner) | squid | No fix yet | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 9 | squid | 7:5.5-6.0.1.el9_3.5 | ELSA-2024-0071 |
| Oracle Linux 8 | libecap +1 | 1.0.1-2.module+el8.9.0+90083+f7556140 | ELSA-2024-0046 |
| Oracle Linux 8 | squid | 7:4.15-7.module+el8.9.0+90111+615ac445.5 | ELSA-2024-0046 |
| Oracle Linux 7 | squid +2 | 7:3.5.20-17.0.1.el7_9.10 | ELSA-2024-1787 |
Advisories 24
- ALSA-2024:0071 Important: squid security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2024:0046 Important: squid:4 security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2024:1153 Red Hat Security Advisory: squid security update Red Hat Security Advisories (RHSA) · Jul 12, 2026
- RHSA-2024:0772 Red Hat Security Advisory: squid:4 security update Red Hat Security Advisories (RHSA) · Jul 12, 2026
- RHSA-2024:0773 Red Hat Security Advisory: squid:4 security update Red Hat Security Advisories (RHSA) · Jul 12, 2026
- RHSA-2024:0771 Red Hat Security Advisory: squid:4 security update Red Hat Security Advisories (RHSA) · Jul 12, 2026
- RHSA-2024:0397 Red Hat Security Advisory: squid:4 security update Red Hat Security Advisories (RHSA) · Jul 12, 2026
- RHSA-2024:0072 Red Hat Security Advisory: squid security update Red Hat Security Advisories (RHSA) · Jul 12, 2026
- RHSA-2024:1787 Red Hat Security Advisory: squid security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2024:0071 Red Hat Security Advisory: squid security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2024:0046 Red Hat Security Advisory: squid:4 security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- USN-6500-1 squid vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- DSA-5637-1 squid - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2024:0046 Important: squid:4 security update Rocky Linux Security Advisories · Feb 5, 2026
- openSUSE-SU-2024:13398-1 squid-6.4-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2023:4380-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2023:4384-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2023:4381-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- WID-SEC-2023-2801 Squid: Schwachstelle ermöglicht Denial of Service BSI CERT-Bund (WID) · Nov 18, 2025
- ELSA-2024-1787 Important: squid security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Apr 11, 2024
- ELSA-2024-0071 Important: squid security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Jan 10, 2024
- ELSA-2024-0046 Important: squid:4 security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Jan 4, 2024
- ALAS2023-2023-429 Important: squid security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Dec 6, 2023
- ALAS2-2023-2354 Important: squid security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Dec 4, 2023
References
- https://github.com/squid-cache/squid/security/advisories/GHSA-73m6-jm96-c6r3
- https://github.com/squid-cache/squid/commit/b70f864940225dfe69f9f653f948e787f99c3810
- http://www.squid-cache.org/Versions/v5/SQUID-2023_4.patch
- http://www.squid-cache.org/Versions/v6/SQUID-2023_4.patch
- https://security.netapp.com/advisory/ntap-20231208-0001/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MEV66D3PAAY6K7TWDT3WZBLCPLASFJDC/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/A5QASTMCUSUEW3UOMKHZJB3FTONWSRXS/