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Fencer Vulns
high 7.5

CVE-2020-11653 json

An issue was discovered in Varnish Cache before 6.0.6 LTS, 6.1.x and 6.2.x before 6.2.3, and 6.3.x before 6.3.2.

published 2020-04-08 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-3996

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.2%
EPSS 2.2% chance of exploitation in 30 days, percentile 82%
public exploits
0
none known

Summary

An issue was discovered in Varnish Cache before 6.0.6 LTS, 6.1.x and 6.2.x before 6.2.3, and 6.3.x before 6.3.2. It occurs when communication with a TLS termination proxy uses PROXY version 2. There can be an assertion failure and daemon restart, which causes a performance loss.

Patch / fix

  • varnish-cache varnish_cache 6.2.3, 6.3.2
  • varnish-software varnish_cache 6.0.6
  • varnish Debian 13, Debian 12 6.4.0-1

debian advisories DEBIAN-CVE-2020-11653

  • varnish Ubuntu 20.04 LTS 6.2.1-2ubuntu0.1

ubuntu advisories UBUNTU-CVE-2020-11653

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • varnish RHEL 8 6.0.6-2.module+el8.3.0+6843+b3b42fcc
  • varnish-modules RHEL 8 0.15.0-5.module+el8.3.0+6843+b3b42fcc

red hat advisories RHSA-2020:4756

  • varnish Package Hub 15 SP1 6.2.1-bp151.4.6.1
  • varnish openSUSE Leap 15.1 6.2.1-lp151.3.6.1

opensuse advisories openSUSE-SU-2020:0819-1openSUSE-SU-2020:0808-1

  • varnish Rocky Linux 8 6.0.6-2.module+el8.3.0+179+20b582cc
  • varnish-modules Rocky Linux 8 0.15.0-5.module+el8.3.0+179+20b582cc

rocky linux advisories RLSA-2020:4756

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-11653 updated cvss 7.5

varnish: remote clients may cause Varnish to assert and restart which could result in DoS

  • Red Hat Software Collections rh-varnish5-varnish, rh-varnish6-varnish, rh-varnish5-varnish-libs, rh-varnish6-varnish-libs
    affected: workaround, no fix available, no fix planned “An user can mitigate the problem by setting the proxy protocol to version 1 on the TLS Proxy side, as this flaw only affects the proxy protocol version 2.”
  • Red Hat Enterprise Linux AppStream (v. 8) varnish 6.0.6-2.module+el8.3.0+6843+b3b42fcc, varnish-modules 0.15.0-5.module+el8.3.0+6843+b3b42fcc
    fixed: vendor fix “An user can mitigate the problem by setting the proxy protocol to version 1 on the TLS Proxy side, as this flaw only affects the proxy protocol version 2.” RHSA-2020:4756

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.16% chance of exploitation in the next 30 days, higher than 82% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.