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CVE-2016-4556

Double free vulnerability in Esi.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows...

7.5 HighFix available

Double free vulnerability in Esi.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows remote servers to cause a denial of service (crash) via a crafted Edge Side Includes (ESI) response.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

23.1%Up 20.4 points since Feb 4, 2022
90%50%10%1%

What each source reports

NVD Score used 7.5

Double free vulnerability in Esi.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows remote servers to cause a denial of service (crash) via a crafted Edge Side Includes (ESI) response.

Record
CVE-2016-4556
CVSS 3.0
7.5 HighCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0
5.0 MediumAV:N/AC:L/Au:N/C:N/I:N/A:P
Updated
2026-11-02
CVE List No score

Double free vulnerability in Esi.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows remote servers to cause a denial of service (crash) via a crafted Edge Side Includes (ESI) response.

Record
CVE-2016-4556
Updated
2026-11-02
EUVDEUVD-2016-5543 No score

Double free vulnerability in Esi.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows remote servers to cause a denial of service (crash) via a crafted Edge Side Includes (ESI) response.

Record
EUVD-2016-5543
Updated
2026-11-03
GitHub AdvisoriesGHSA-2xhq-835p-4pg5 7.5

Double free vulnerability in Esi.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows...

Double free vulnerability in Esi.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows remote servers to cause a denial of service (crash) via a crafted Edge Side Includes (ESI) response.

Record
GHSA-2xhq-835p-4pg5
CVSS 3.0
7.5 HighCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSV 7.5

Double free vulnerability in Esi.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows remote servers to cause a denial of service (crash) via a crafted Edge Side Includes (ESI) response.

Record
CVE-2016-4556
CVSS 3.0
7.5 HighCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2016-4556 7.5

Double free vulnerability in Esi.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows remote servers to cause a denial of service (crash) via a crafted Edge Side Includes (ESI) response.

Record
UBUNTU-CVE-2016-4556
CVSS 3.0
7.5 HighCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVSUSE-SU-2016:2008-1 No score

Security update for squid

The Squid HTTP proxy has been updated to version 3.3.14, fixing the following security issues:

  • Fixed multiple Denial of Service issues in HTTP Response processing. (CVE-2016-2569, CVE-2016-2570, CVE-2016-2571, CVE-2016-2572, bsc#968392, bsc#968393, bsc#968394, bsc#968395)
  • CVE-2016-3947: Buffer overrun issue in pinger ICMPv6 processing. (bsc#973782)
  • CVE-2015-5400: Improper protection of alternate path. (bsc#938715)
  • CVE-2015-3455: Squid http proxy configured with client-first SSL bumping did not correctly validate server certificate. (bsc#929493)
  • CVE-2016-3948: Fixed denial of service in HTTP Response processing (bsc#973783)
  • CVE-2016-4051: fixes buffer overflow in cachemgr.cgi (bsc#976553)
  • CVE-2016-4052, CVE-2016-4053, CVE-2016-4054: Fixed multiple issues in ESI processing (bsc#976556)
  • CVE-2016-4553: Fixed cache poisoning issue in HTTP Request handling (bsc#979009)
  • CVE-2016-4554: Fixed header smuggling issue in HTTP Request processing (bsc#979010)
  • Fixed multiple Denial of Service issues in ESI Response processing. (CVE-2016-4555, CVE-2016-4556, bsc#979011, bsc#979008)

Additionally, the following non-security issues have been fixed:

  • Fix header size in script unsquid.pl. (bsc#902197)
  • Add external helper ext_session_acl to package. (bsc#959290)
  • Update forward_max_tries to permit 25 server paths With cloud sites becoming more popular more CDN servers are producing long lists of IPv6 and IPv4 addresses. If there are not enough paths selected the IPv4 ones may never be reached.
  • squid.init: wait that squid really dies when we kill it on upgrade instead of proclaiming its demise prematurely (bnc#963539)
Record
SUSE-SU-2016:2008-1
Updated
2026-11-02
OSVSUSE-SU-2016:2089-1 No score

Security update for squid3

This update for squid3 fixes the following issues:

  • Multiple issues in pinger ICMP processing. (CVE-2014-7141, CVE-2014-7142)

  • CVE-2016-3947: Buffer overrun issue in pinger ICMPv6 processing. (bsc#973782)

  • CVE-2016-4554: fix header smuggling issue in HTTP Request processing (bsc#979010)

  • Fix multiple Denial of Service issues in HTTP Response processing. (CVE-2016-2569, CVE-2016-2570, CVE-2016-2571, CVE-2016-2572, bsc#968392, bsc#968393, bsc#968394, bsc#968395)

  • Regression caused by the DoS fixes above (bsc#993299)

  • CVE-2016-3948: Fix denial of service in HTTP Response processing (bsc#973783)

  • CVE-2016-4051: fixes buffer overflow in cachemgr.cgi (bsc#976553)

  • CVE-2016-4052, CVE-2016-4053, CVE-2016-4054:

    • fixes multiple issues in ESI processing (bsc#976556)
  • CVE-2016-4556: fixes double free vulnerability in Esi.cc (bsc#979008)

  • CVE-2015-5400: Improper Protection of Alternate Path (bsc#938715)

  • CVE-2014-6270: fix off-by-one in snmp subsystem (bsc#895773)

  • Memory leak in squid3 when using external_acl (bsc#976708)

Record
SUSE-SU-2016:2089-1
Updated
2026-11-02
OSVUSN-2995-1 No score

squid3 vulnerabilities

Yuriy M. Kaminskiy discovered that the Squid pinger utility incorrectly handled certain ICMPv6 packets. A remote attacker could use this issue to cause Squid to crash, resulting in a denial of service, or possibly cause Squid to leak information into log files. (CVE-2016-3947)

Yuriy M. Kaminskiy discovered that the Squid cachemgr.cgi tool incorrectly handled certain crafted data. A remote attacker could use this issue to cause Squid to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2016-4051)

It was discovered that Squid incorrectly handled certain Edge Side Includes (ESI) responses. A remote attacker could possibly use this issue to cause Squid to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2016-4052, CVE-2016-4053, CVE-2016-4054)

Jianjun Chen discovered that Squid did not correctly ignore the Host header when absolute-URI is provided. A remote attacker could possibly use this issue to conduct cache-poisoning attacks. This issue only affected Ubuntu 14.04 LTS, Ubuntu 15.10 and Ubuntu 16.04 LTS. (CVE-2016-4553)

Jianjun Chen discovered that Squid incorrectly handled certain HTTP Host headers. A remote attacker could possibly use this issue to conduct cache-poisoning attacks. (CVE-2016-4554)

It was discovered that Squid incorrectly handled certain Edge Side Includes (ESI) responses. A remote attacker could possibly use this issue to cause Squid to crash, resulting in a denial of service. (CVE-2016-4555, CVE-2016-4556)

Record
USN-2995-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
squid3
Debian:7
before 3.1.20-2.2+deb7u5, plus listed versions
3.1.20-2.23.1.20-2.2+deb7u13.1.20-2.2+deb7u23.1.20-2.2+deb7u33.1.20-2.2+deb7u4
3.1.20-2.2+deb7u5
squid3
Debian:8
before 3.4.8-6+deb8u3, plus listed versions
3.4.8-63.4.8-6+deb8u13.4.8-6+deb8u23.4.8-6+deb8u2~bpo70+1
3.4.8-6+deb8u3
squid
Red Hat:enterprise_linux:6::server
before 7:3.1.23-16.el6_8.4
7:3.1.23-16.el6_8.4
squid-debuginfo
Red Hat:enterprise_linux:6::server
before 7:3.1.23-16.el6_8.4
7:3.1.23-16.el6_8.4
squid
Red Hat:enterprise_linux:6::workstation
before 7:3.1.23-16.el6_8.4
7:3.1.23-16.el6_8.4
squid-debuginfo
Red Hat:enterprise_linux:6::workstation
before 7:3.1.23-16.el6_8.4
7:3.1.23-16.el6_8.4
squid
Red Hat:enterprise_linux:7::server
before 7:3.3.8-26.el7_2.3
7:3.3.8-26.el7_2.3
squid-debuginfo
Red Hat:enterprise_linux:7::server
before 7:3.3.8-26.el7_2.3
7:3.3.8-26.el7_2.3
squid-sysvinit
Red Hat:enterprise_linux:7::server
before 7:3.3.8-26.el7_2.3
7:3.3.8-26.el7_2.3
squid
Red Hat:enterprise_linux:7::workstation
before 7:3.3.8-26.el7_2.3
7:3.3.8-26.el7_2.3
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Affected packages
PackageAffectedFixed
squid-debuginfo
Red Hat:enterprise_linux:7::workstation
before 7:3.3.8-26.el7_2.3
7:3.3.8-26.el7_2.3
squid-sysvinit
Red Hat:enterprise_linux:7::workstation
before 7:3.3.8-26.el7_2.3
7:3.3.8-26.el7_2.3
squid34
Red Hat:enterprise_linux:6::server
before 7:3.4.14-9.el6_8.3
7:3.4.14-9.el6_8.3
squid34-debuginfo
Red Hat:enterprise_linux:6::server
before 7:3.4.14-9.el6_8.3
7:3.4.14-9.el6_8.3
squid34
Red Hat:enterprise_linux:6::workstation
before 7:3.4.14-9.el6_8.3
7:3.4.14-9.el6_8.3
squid34-debuginfo
Red Hat:enterprise_linux:6::workstation
before 7:3.4.14-9.el6_8.3
7:3.4.14-9.el6_8.3
squid
SUSE:Linux Enterprise Server 12 SP1
before 3.3.14-20.2
3.3.14-20.2
squid
SUSE:Linux Enterprise Server for SAP Applications 12 SP1
before 3.3.14-20.2
3.3.14-20.2
squid3
SUSE:Linux Enterprise Server 11 SP4
before 3.1.23-8.16.30.1
3.1.23-8.16.30.1
squid3
SUSE:Linux Enterprise Server for SAP Applications 11 SP4
before 3.1.23-8.16.30.1
3.1.23-8.16.30.1
squid3
Ubuntu:14.04:LTS
before 3.3.8-1ubuntu6.8, plus listed versions
3.3.8-1ubuntu33.3.8-1ubuntu43.3.8-1ubuntu53.3.8-1ubuntu63.3.8-1ubuntu6.1
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3.3.8-1ubuntu6.23.3.8-1ubuntu6.33.3.8-1ubuntu6.43.3.8-1ubuntu6.6
3.3.8-1ubuntu6.8
squid3
Ubuntu:16.04:LTS
before 3.5.12-1ubuntu7.2, plus listed versions
3.3.8-1ubuntu163.3.8-1ubuntu173.5.12-1ubuntu63.5.12-1ubuntu73.5.12-1ubuntu7.1
3.5.12-1ubuntu7.2

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2016-4556 is a high vulnerability (CVSS 7.5) in Squid-cache Squid, published May 10, 2016. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 23.1%, the 97th percentile. Fixed in squid3 3.1.20-2.2+deb7u5.

References

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