Description
An issue was discovered in Squid 2.x through 2.7.STABLE9, 3.x through 3.5.28, and 4.x through 4.7. When Squid is configured to use Basic Authentication, the Proxy-Authorization header is parsed via uudecode. uudecode determines how many bytes will be decoded by iterating over the input and checking its table. The length is then used to start decoding the string. There are no checks to ensure that the length it calculates isn't greater than the input buffer. This leads to adjacent memory being decoded as well. An attacker would not be able to retrieve the decoded data unless the Squid maintainer had configured the display of usernames on error pages.
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 | 4.8-1 | — |
| Debian 13 | squid | 4.8-1 | — |
| Debian 12 | squid | 4.8-1 | — |
| Debian 10 | squid | 4.6-1+deb10u1 | DSA-4507-1 |
| Debian 9 | squid3 | 3.5.23-5+deb9u2 | DLA-2278-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 8 | squid3 | 3.4.8-6+deb8u8 | DLA-1858-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | squid3 | 3.5.27-1ubuntu1.3 | USN-4065-1 |
| Ubuntu 16.04 LTS | squid3 | 3.5.12-1ubuntu7.8 | USN-4065-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2020:4743 |
| RHEL 8 | squid | 7:4.11-3.module+el8.3.0+7851+7808b5f9 | RHSA-2020:4743 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | libecap +1 | 1.0.1-2.module_el8.6.0+2741+01592ae8 | ALSA-2020:4743 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | libecap | 1.0.1-2.module+el8.4.0+404+316a0dc5 | RLSA-2020:4743 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP1 | squid | 4.9-5.11.1 | SUSE-SU-2019:2975-1 |
| SLES 15 | squid | 4.9-5.11.1 | SUSE-SU-2019:2975-1 |
| SLES 12 SP4 | squid | 3.5.21-26.17.1 | SUSE-SU-2019:2089-1 |
| SLES 12 SP3 | squid | 3.5.21-26.17.1 | SUSE-SU-2019:2089-1 |
| SLES 12 SP2 | squid | 3.5.21-26.17.1 | SUSE-SU-2019:2089-1 |
Show 11 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 11 SP4 | squid3 | 3.1.23-8.16.37.12.1 | SUSE-SU-2020:14460-1 |
| SLES for SAP 12 SP4 | squid | 3.5.21-26.17.1 | SUSE-SU-2019:2089-1 |
| SLES for SAP 12 SP3 | squid | 3.5.21-26.17.1 | SUSE-SU-2019:2089-1 |
| SLES for SAP 12 SP2 | squid | 3.5.21-26.17.1 | SUSE-SU-2019:2089-1 |
| SUSE OpenStack Cloud Crowbar 8 | squid | 3.5.21-26.17.1 | SUSE-SU-2019:2089-2 |
| SUSE OpenStack Cloud 8 | squid | 3.5.21-26.17.1 | SUSE-SU-2019:2089-1 |
| SUSE OpenStack Cloud 7 | squid | 3.5.21-26.17.1 | SUSE-SU-2019:2089-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | squid3 | 3.1.23-8.16.37.12.1 | SUSE-SU-2020:14460-1 |
| SUSE HPE Helion OpenStack 8 | squid | 3.5.21-26.17.1 | SUSE-SU-2019:2089-2 |
| SUSE Enterprise Storage 5 | squid | 3.5.21-26.17.1 | SUSE-SU-2019:2089-2, SUSE-SU-2019:2089-1 |
| SUSE Enterprise Storage 4 | squid | 3.5.21-26.17.1 | SUSE-SU-2019:2089-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | squid | 4.16-1.5 | openSUSE-SU-2024:11403-1 |
| openSUSE Leap 15.1 | squid | 4.9-lp151.2.7.1 | openSUSE-SU-2019:2541-1 |
| openSUSE Leap 15.0 | squid | 4.9-lp150.13.1 | openSUSE-SU-2019:2540-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.10 | squid | 4.8-r0 | — |
| Alpine v3.9 | squid | 4.8-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | squid +2 | 7:3.5.20-17.amzn2.7.10 | ALAS2-2023-2318 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | libecap +1 | 1.0.1-2.module+el8.3.0+7819+eb7d4ef6 | ELSA-2020-4743 |
| Oracle Linux 8 | squid | 7:4.11-3.module+el8.3.0+7819+eb7d4ef6 | ELSA-2020-4743 |
Advisories 17
- ALSA-2020:4743 Moderate: squid:4 security, bug fix, and enhancement update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2020:4743 Red Hat Security Advisory: squid:4 security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Jul 4, 2026
- DSA-4507-1 squid - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-1858-1 squid3 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2278-1 squid3 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- USN-4065-1 squid, squid3 vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026
- RLSA-2020:4743 Moderate: squid:4 security, bug fix, and enhancement update Rocky Linux Security Advisories · Feb 4, 2026
- SUSE-SU-2019:2089-2 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:11403-1 squid-4.16-1.5 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2019:2541-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2019:2975-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2019:2540-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2019:2089-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:14460-1 Security update for squid3 SUSE / openSUSE Security Updates · May 2, 2025
- ALAS2-2023-2318 Critical: squid security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Nov 6, 2023
- WID-SEC-2023-2486 Squid: Mehrere Schwachstellen BSI CERT-Bund (WID) · Oct 26, 2023
- ELSA-2020-4743 Moderate: squid:4 security, bug fix, and enhancement update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 10, 2020
References
- http://www.squid-cache.org/Versions/v4/changesets/
- https://github.com/squid-cache/squid/commits/v4
- http://www.squid-cache.org/Versions/v4/changesets/squid-4-dd46b5417809647f561d8a5e0e74c3aacd235258.patch
- USN-4065-1 vendor-advisory
- [debian-lts-announce] 20190720 [SECURITY] [DLA 1858-1] squid3 security update mailing-list
- USN-4065-2 vendor-advisory
- FEDORA-2019-cb50bcc189 vendor-advisory
- DSA-4507 vendor-advisory
- 20190825 [SECURITY] [DSA 4507-1] squid security update mailing-list
- openSUSE-SU-2019:2540 vendor-advisory
- openSUSE-SU-2019:2541 vendor-advisory
- [debian-lts-announce] 20200710 [SECURITY] [DLA 2278-1] squid3 security update mailing-list