CVE catalog

CVE-2020-15811

squid: CVE-2020-15811

Severity: Critical · CVSS 9.6CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
Published: Aug 23, 2020, 10:00:00 PM UTC
Source: [NVD] · [CVE record]
EPSS: 4.07% · Oct 25, 2026

An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Splitting attacks may succeed against HTTP and HTTPS traffic. This leads to cache poisoning. This allows any client, including browser scripts, to bypass local security and poison the browser cache and any downstream caches with content from an arbitrary source. Squid uses a string search instead of parsing the Transfer-Encoding header to find chunked encoding. This allows an attacker to hide a second request inside Transfer-Encoding: it is interpreted by Squid as chunked and split out into a second request delivered upstream. Squid will then deliver two distinct responses to the client, corrupting any downstream caches.

Vulnerable and fixed packages

Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.

Distribution	Package	Release	Version	Status
Debian	squid	sid	`7.7-1`	fixed
Debian	squid	forky	`7.7-1`	fixed
Debian	squid	trixie	`6.13-2+deb13u3`	fixed
Debian	squid	trixie-security	`6.13-2+deb13u2`	fixed
Debian	squid	bookworm	`5.7-2+deb12u5`	fixed
Debian	squid	bookworm-security	`5.7-2+deb12u6`	fixed
Alpine	squid	3.10	`4.13-r0`	fixed
Alpine	squid	3.11	`4.13-r0`	fixed
Alpine	squid	3.12	`4.13-r0`	fixed
Alpine	squid	3.13	`4.13.0-r0`	fixed
Alpine	squid	3.14	`4.13.0-r0`	fixed
Alpine	squid	3.15	`4.13.0-r0`	fixed
Alpine	squid	3.16	`4.13.0-r0`	fixed
Alpine	squid	3.17	`4.13.0-r0`	fixed
Alpine	squid	3.18	`4.13.0-r0`	fixed
Alpine	squid	3.19	`4.13.0-r0`	fixed
Alpine	squid	3.20	`4.13.0-r0`	fixed
Alpine	squid	3.21	`4.13.0-r0`	fixed
Alpine	squid	3.22	`4.13.0-r0`	fixed
Alpine	squid	3.23	`4.13.0-r0`	fixed
Alpine	squid	3.24	`4.13.0-r0`	fixed
Alpine	squid	3.9	`4.13-r0`	fixed
Ubuntu	squid3	16.04	`3.3.8-1ubuntu16`	vulnerable
Ubuntu	squid3	16.04	`3.3.8-1ubuntu17`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu6`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.1`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.2`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.3`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.4`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.5`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.6`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.7`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.8`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.9`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.10`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.11`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.12`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.13`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.14`	vulnerable
Ubuntu	squid3	16.04	`3.5.12-1ubuntu7.15`	fixed
Ubuntu	squid3	18.04	`3.5.23-5ubuntu1`	vulnerable
Ubuntu	squid3	18.04	`3.5.23-5ubuntu2`	vulnerable
Ubuntu	squid3	18.04	`3.5.27-1ubuntu1`	vulnerable
Ubuntu	squid3	18.04	`3.5.27-1ubuntu1.1`	vulnerable
Ubuntu	squid3	18.04	`3.5.27-1ubuntu1.2`	vulnerable
Ubuntu	squid3	18.04	`3.5.27-1ubuntu1.3`	vulnerable
Ubuntu	squid3	18.04	`3.5.27-1ubuntu1.4`	vulnerable
Ubuntu	squid3	18.04	`3.5.27-1ubuntu1.5`	vulnerable
Ubuntu	squid3	18.04	`3.5.27-1ubuntu1.6`	vulnerable
Ubuntu	squid3	18.04	`3.5.27-1ubuntu1.7`	vulnerable
Ubuntu	squid3	18.04	`3.5.27-1ubuntu1.8`	vulnerable
Ubuntu	squid3	18.04	`3.5.27-1ubuntu1.9`	fixed
Ubuntu	squid	20.04	`4.8-1ubuntu2`	vulnerable
Ubuntu	squid	20.04	`4.8-1ubuntu3`	vulnerable
Ubuntu	squid	20.04	`4.9-2ubuntu1`	vulnerable
Ubuntu	squid	20.04	`4.9-2ubuntu2`	vulnerable
Ubuntu	squid	20.04	`4.9-2ubuntu3`	vulnerable
Ubuntu	squid	20.04	`4.9-2ubuntu4`	vulnerable
Ubuntu	squid	20.04	`4.10-1ubuntu1`	vulnerable
Ubuntu	squid	20.04	`4.10-1ubuntu1.1`	vulnerable
Ubuntu	squid	20.04	`4.10-1ubuntu1.2`	fixed

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	squid	source	sid	`4.13-1`	not yet assigned	Not reported	[968932]
Debian	squid	source	forky	`4.13-1`	not yet assigned	Not reported	[968932]
Debian	squid	source	trixie	`4.13-1`	not yet assigned	Not reported	[968932]
Debian	squid	source	bookworm	`4.13-1`	not yet assigned	Not reported	[968932]
Alpine	squid	apk	3.10	`4.13-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.11	`4.13-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.12	`4.13-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.13	`4.13.0-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.14	`4.13.0-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.15	`4.13.0-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.16	`4.13.0-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.17	`4.13.0-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.18	`4.13.0-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.19	`4.13.0-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.20	`4.13.0-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.21	`4.13.0-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.22	`4.13.0-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.23	`4.13.0-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.24	`4.13.0-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Alpine	squid	apk	3.9	`4.13-r0`	Not reported	ALPINE-CVE-2020-15811	Not reported
Ubuntu	squid3	deb	16.04	`3.5.12-1ubuntu7.15`	Not reported	UBUNTU-CVE-2020-15811	Not reported
Ubuntu	squid3	deb	18.04	`3.5.27-1ubuntu1.9`	Not reported	UBUNTU-CVE-2020-15811	Not reported
Ubuntu	squid	deb	20.04	`4.10-1ubuntu1.2`	Not reported	UBUNTU-CVE-2020-15811	Not reported

[Debian bug #968932]

OpenFactory catalog packages

Matching against OpenFactory catalog package versions is in progress.

[Debian 12 (Bookworm)]

[squid]Unknown
Details (4)
- 5.7-2+deb12u5 · amd64 · bookworm
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u5 · arm64 · bookworm
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u6 · amd64 · bookworm-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u6 · arm64 · bookworm-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
[squid-cgi]Unknown
Source package: [squid]
Details (4)
- 5.7-2+deb12u5 · amd64 · bookworm
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u5 · arm64 · bookworm
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u6 · amd64 · bookworm-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u6 · arm64 · bookworm-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
[squidclient]Unknown
Source package: [squid]
Details (4)
- 5.7-2+deb12u5 · amd64 · bookworm
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u5 · arm64 · bookworm
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u6 · amd64 · bookworm-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u6 · arm64 · bookworm-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
[squid-common]Unknown
Source package: [squid]
Details (4)
- 5.7-2+deb12u5 · all · bookworm
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u5 · all · bookworm
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u6 · all · bookworm-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u6 · all · bookworm-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
[squid-openssl]Unknown
Source package: [squid]
Details (4)
- 5.7-2+deb12u5 · amd64 · bookworm
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u5 · arm64 · bookworm
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u6 · amd64 · bookworm-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u6 · arm64 · bookworm-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
[squid-purge]Unknown
Source package: [squid]
Details (4)
- 5.7-2+deb12u5 · amd64 · bookworm
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u5 · arm64 · bookworm
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u6 · amd64 · bookworm-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12
- 5.7-2+deb12u6 · arm64 · bookworm-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · bookworm; dsa · squid · debian · 12

[Debian 13 (Trixie)]

[squid]Unknown
Details (4)
- 6.13-2+deb13u2 · amd64 · trixie
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · arm64 · trixie
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · amd64 · trixie-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · arm64 · trixie-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
[squid-cgi]Unknown
Source package: [squid]
Details (4)
- 6.13-2+deb13u2 · amd64 · trixie
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · arm64 · trixie
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · amd64 · trixie-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · arm64 · trixie-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
[squidclient]Unknown
Source package: [squid]
Details (4)
- 6.13-2+deb13u2 · amd64 · trixie
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · arm64 · trixie
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · amd64 · trixie-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · arm64 · trixie-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
[squid-common]Unknown
Source package: [squid]
Details (4)
- 6.13-2+deb13u2 · all · trixie
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · all · trixie
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · all · trixie-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · all · trixie-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
[squid-openssl]Unknown
Source package: [squid]
Details (4)
- 6.13-2+deb13u2 · amd64 · trixie
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · arm64 · trixie
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · amd64 · trixie-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · arm64 · trixie-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
[squid-purge]Unknown
Source package: [squid]
Details (4)
- 6.13-2+deb13u2 · amd64 · trixie
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · arm64 · trixie
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · amd64 · trixie-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13
- 6.13-2+deb13u2 · arm64 · trixie-security
  Fixed · Fixed: 4.13-1
  dsa · squid · debian · 13

Observed: Oct 23, 2026, 5:48:27 PM UTC

References

[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]