Description
An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. An integer overflow problem allows a remote server to achieve Denial of Service when delivering responses to HTTP Range requests. The issue trigger is a header that can be expected to exist in HTTP traffic without any malicious intent.
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 | 4.13-10 | — |
| Debian 13 | squid | 4.13-10 | — |
| Debian 12 | squid | 4.13-10 | — |
| Debian 10 | squid | 4.6-1+deb10u6 | DSA-4924-1 |
| Debian 9 | squid3 | 3.5.23-5+deb9u7 | DLA-2685-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | squid | 4.10-1ubuntu1.4 | USN-4981-1 |
| Ubuntu 18.04 LTS | squid3 | 3.5.27-1ubuntu1.11 | USN-4981-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 16.04 LTS | squid3 | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2021:4292 |
| RHEL 8 | squid | 7:4.15-1.module+el8.5.0+11469+24c223d9 | RHSA-2021:4292 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | libecap +1 | 1.0.1-2.module_el8.6.0+2741+01592ae8 | ALSA-2021:4292 |
| AlmaLinux 8 | squid | 7:4.15-3.module_el8.6.0+3010+383bc947.1 | ALSA-2021:4292 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | libecap | 1.0.1-2.module+el8.4.0+404+316a0dc5 | RLSA-2021:4292 |
| Rocky Linux 8 | squid | 7:4.15-1.module+el8.5.0+705+218dec94 | RLSA-2021:4292 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | squid | 5.0.6-r0 | — |
| Alpine v3.23 | squid | 5.0.6-r0 | — |
| Alpine v3.22 | squid | 5.0.6-r0 | — |
| Alpine v3.21 | squid | 5.0.6-r0 | — |
| Alpine v3.20 | squid | 5.0.6-r0 | — |
Show 10 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | squid | 5.0.6-r0 | — |
| Alpine v3.18 | squid | 5.0.6-r0 | — |
| Alpine v3.17 | squid | 5.0.6-r0 | — |
| Alpine v3.16 | squid | 5.0.6-r0 | — |
| Alpine v3.15 | squid | 5.0.6-r0 | — |
| Alpine v3.14 | squid | 5.0.6-r0 | — |
| Alpine v3.13 | squid | 5.0.6-r0 | — |
| Alpine v3.12 | squid | 4.15-r0 | — |
| Alpine v3.11 | squid | 4.15-r0 | — |
| Alpine v3.10 | squid | 4.15-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | squid +2 | 7:3.5.20-17.amzn2.7.2 | ALAS2-2023-1950 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | libecap +1 | 1.0.1-2.module+el8.3.0+7819+eb7d4ef6 | ELSA-2021-4292 |
| Oracle Linux 8 | squid | 7:4.15-1.module+el8.5.0+20327+24c223d9 | ELSA-2021-4292 |
| Oracle Linux 7 | squid +2 | 7:3.5.20-17.0.1.el7_9.6 | ELSA-2021-9465 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.
Metasploit 1 module
-
Squid Proxy Range Header DoS
auxiliary/dos/http/squid_range_dos
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 10
- ALSA-2021:4292 Moderate: squid:4 security, bug fix, and enhancement update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2021:4292 Red Hat Security Advisory: squid:4 security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Jun 27, 2026
- USN-4981-1 squid, squid3 vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- DSA-4924-1 squid - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2685-1 squid3 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2021:4292 Moderate: squid:4 security, bug fix, and enhancement update Rocky Linux Security Advisories · Feb 4, 2026
- WID-SEC-2023-0456 Squid: Schwachstelle ermöglicht Denial of Service BSI CERT-Bund (WID) · Sep 27, 2023
- ALAS2-2023-1950 Moderate: squid security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Feb 22, 2023
- ELSA-2021-4292 Moderate: squid:4 security, bug fix, and enhancement update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 16, 2021
- ELSA-2021-9465 Important: squid security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Sep 24, 2021
References
- https://github.com/squid-cache/squid/security/advisories/GHSA-pxwq-f3qr-w2xf
- http://www.squid-cache.org/Versions/v4/changesets/squid-4-e7cf864f938f24eea8af0692c04d16790983c823.patch
- FEDORA-2021-c0bec55ec7 vendor-advisory
- FEDORA-2021-24af72ff2c vendor-advisory
- [debian-lts-announce] 20210614 [SECURITY] [DLA 2685-1] squid3 security update mailing-list
- https://security.netapp.com/advisory/ntap-20210716-0007/
- [oss-security] 20231011 Squid Caching Proxy Security Audit: 55 Vulnerabilities, 35 0days. mailing-list
- 20231016 Squid Caching Proxy Security Audit: 55 Vulnerabilities, 35 0days. mailing-list