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Fencer Vulns
medium 5.3

CVE-2019-18678 json

An issue was discovered in Squid 3.x and 4.x through 4.8.

published 2019-11-26 6 y ago modified 2026-06-17 4 mo ago also EUVD-2019-8394

cvss
5.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
6.2%
EPSS 6.2% chance of exploitation in 30 days, percentile 93%
public exploits
0
none known

Summary

An issue was discovered in Squid 3.x and 4.x through 4.8. It allows attackers to smuggle HTTP requests through frontend software to a Squid instance that splits the HTTP Request pipeline differently. The resulting Response messages corrupt caches (between a client and Squid) with attacker-controlled content at arbitrary URLs. Effects are isolated to software between the attacker client and Squid. There are no effects on Squid itself, nor on any upstream servers. The issue is related to a request header containing whitespace between a header name and a colon.

Patch / fix

  • squid Debian 14, Debian 13, Debian 12 4.9-1

debian advisories DEBIAN-CVE-2019-18678

  • squid Ubuntu 20.04 LTS 4.9-2ubuntu1
  • squid3 Ubuntu 16.04 LTS 3.5.12-1ubuntu7.9
  • squid3 Ubuntu 18.04 LTS 3.5.27-1ubuntu1.4

ubuntu advisories UBUNTU-CVE-2019-18678

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

  • squid RHEL 8 7:4.11-3.module+el8.3.0+7851+7808b5f9
  • libecap RHEL 8 1.0.1-2.module+el8.1.0+4044+36416a77

red hat advisories RHSA-2020:4743

  • squid3 SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 3.1.23-8.16.37.12.1
  • squid SLES for SAP 12 SP4, SLES for SAP 12 SP3, SLES for SAP 12 SP2 +10 more 3.5.21-26.20.1
  • squid SLES for SAP 12 SP5, SLES 12 SP5 4.9-4.3.2
  • squid SLE Module for Server Applications 15 SP1, SLE Module for Server Applications 15 4.9-5.11.1

suse advisories SUSE-SU-2020:14460-1SUSE-SU-2020:0661-1SUSE-SU-2019:3067-1SUSE-SU-2019:2975-1

  • squid openSUSE Tumbleweed 4.16-1.5
  • squid openSUSE Leap 15.1 4.9-lp151.2.7.1
  • squid openSUSE Leap 15.0 4.9-lp150.13.1

opensuse advisories openSUSE-SU-2024:11403-1openSUSE-SU-2019:2541-1openSUSE-SU-2019:2540-1

  • libecap AlmaLinux 8 1.0.1-2.module_el8.6.0+2741+01592ae8

almalinux advisories ALSA-2020:4743

  • libecap Rocky Linux 8 1.0.1-2.module+el8.4.0+404+316a0dc5

rocky linux advisories RLSA-2020:4743

  • squid Arch Linux 4.9-1

arch linux advisories AVG-1062

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-2019-18678 updated cvss 6.8

squid: HTTP Request Splitting issue in HTTP message processing

  • Red Hat Enterprise Linux 6 squid, squid34
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 squid, squid-sysvinit, squid-migration-script
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux AppStream (v. 8) squid 4.11-3.module+el8.3.0+7851+7808b5f9, libecap 1.0.1-2.module+el8.1.0+4044+36416a77
    fixed: vendor fix RHSA-2020:4743
  • Red Hat Enterprise Linux 5 squid
    not affected: vulnerable code not present

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

6.20% chance of exploitation in the next 30 days, higher than 93% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N

Classification

Weakness
  • CWE-444 Inconsistent Interpretation of HTTP Requests

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.