CVE-2021-28662
Mediumsquid: denial of service in HTTP response processing
Published Jun 3, 2021 · Updated Aug 4, 2026 · Also known as ALPINE-CVE-2021-28662, DEBIAN-CVE-2021-28662, GHSA-jjq6-mh2h-g39h, UBUNTU-CVE-2021-28662
Key Facts
Patch immediately- CVE-2021-28662 is a medium-severity vulnerability (CVSS 6.5 v3.1) affecting Squid (Squid-Cache), Debian Linux, Fedora (Fedoraproject) and 5 more products.
- It is not listed in any known-exploited vulnerabilities catalog. No public exploit code is known.
- EPSS estimates a 72% probability of exploitation in the next 30 days.
- Fixed versions are available, including libecap 1.0.1-2.module_el8.6.0+2741+01592ae8, libecap 1.0.1-2.module+el8.3.0+7819+eb7d4ef6, libecap 1.0.1-2.module+el8.4.0+404+316a0dc5.
- Brandefense priority: patch immediately, because it is very likely to be exploited soon.
CVSS v3.1
6.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
EPSS (30-day exploit likelihood)
72%
Higher than 99.4% of all scored CVEs
Exploited in the wild
No known
Not in a known-exploited catalog
Public exploit code
None known
Get the full CVE-2021-28662 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
Description
An issue was discovered in Squid 4.x before 4.15 and 5.x before 5.0.6. If a remote server sends a certain response header over HTTP or HTTPS, there is a denial of service. This header can plausibly occur in benign network traffic.
Affected Products
84 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| SquidSquid-Cache | See advisory | 4.15 |
| Debian LinuxDebian | 10.0 | n/a |
| FedoraFedoraproject | 33, 34 | n/a |
| rootio-squidrootio | See advisory | 5.0.6-r0 |
| squid3ubuntu | See advisory | 3.5.27-1ubuntu1.11 |
Patched Releases
libecap
1.0.1-2.module_el8.6.0+2741+01592ae8, 1.0.1-2.module+el8.3.0+7819+eb7d4ef6, 1.0.1-2.module+el8.4.0+404+316a0dc5
libecap-devel
1.0.1-2.module+el8.3.0+7819+eb7d4ef6
rootio-squid
5.0.6-r0
Squid
4.10-1ubuntu1.4, 4.13-10, 4.15-1, 4.15-4.18.1, 4.15-5.26.1, 4.15-lp152.2.9.1, 4.15-r0, 4.16-1.5, 4.16-1.ph3, 4.16-1.ph4, 4.6-1+deb10u6, 5.0.6-r0, 7:4.15-1.module+el8.5.0+20327+24c223d9, 7:4.15-1.module+el8.5.0+705+218dec94, 7:4.15-3.module_el8.6.0+3010+383bc947.1, 4.15
squid:4
8050020210618131503.b4937e53
squid3
3.5.27-1ubuntu1.11
Timeline
Publicly disclosed
Jun 3, 2021
Last updated
Aug 4, 2026
Weakness Type
- CWE-20 Improper Input Validation
- CWE-116 Improper Encoding or Escaping of Output
References
- advisoryRHSA-2021:4292
- advisoryhttps://bugzilla.suse.com/1171164
- advisoryhttps://bugzilla.suse.com/1171569
- advisoryhttps://bugzilla.suse.com/1183436
- advisoryhttps://bugzilla.suse.com/1185916
FAQ
Common Questions.
An issue was discovered in Squid 4.x before 4.15 and 5.x before 5.0.6.
Affected: Squid (Squid-Cache); Debian Linux versions 10.0; Fedora (Fedoraproject) versions 33, 34, among others. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
Fixed versions are available, including libecap 1.0.1-2.module_el8.6.0+2741+01592ae8, libecap 1.0.1-2.module+el8.3.0+7819+eb7d4ef6, libecap 1.0.1-2.module+el8.4.0+404+316a0dc5.
Brandefense priority: patch immediately, because it is very likely to be exploited soon.
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