squid: Incorrect pointer handling in HTTP processing and certificate download can lead to denial of service
Published Feb 9, 2018
7.5
HIGHCVSS 3.0
EPSS 12.91%
Description
The Squid Software Foundation Squid HTTP Caching Proxy version prior to version 4.0.23 contains a NULL Pointer Dereference vulnerability in HTTP Response X-Forwarded-For header processing that can result in Denial of Service to all clients of the proxy. This attack appear to be exploitable via Remote HTTP server responding with an X-Forwarded-For header to certain types of HTTP request. This vulnerability appears to have been fixed in 4.0.23 and later.
Affected products
No data.
Configuration 1
- < 4.0.23
Configuration 2
- 7.0
- 8.0
- 9.0
Configuration 3
- 14.04
- 16.04
- 17.10
No data.
Red Hat Enterprise Linux 7
squid-7:3.5.20-15.el7
Fixed · RHSA-2020:1068
Red Hat Enterprise Linux 5
squid
Not affected
Red Hat Enterprise Linux 6
squid
Will not fix
Red Hat Enterprise Linux 6
squid34
Will not fix
Red Hat Enterprise Linux 8
squid
Not affected
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 7 | squid-7:3.5.20-15.el7 | Fixed | RHSA-2020:1068 |
| Red Hat Enterprise Linux 5 | squid | Not affected | n/a |
| Red Hat Enterprise Linux 6 | squid | Will not fix | n/a |
| Red Hat Enterprise Linux 6 | squid34 | Will not fix | n/a |
| Red Hat Enterprise Linux 8 | squid | Not affected | n/a |
No package ranges for this CVE.
Remediation
Red Hat mitigation
A workaround for this issue is to set the "log_uses_indirect_client off" configuration directive in the squid configuration file (for example /etc/squid/squid.conf).
Metrics
No CVSS v4.0 score for this CVE.
No CVSS v3.1 score for this CVE.
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
1 other source (Red Hat) ▾
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
AV:N/AC:L/Au:N/C:N/I:N/A:P
This CVE is not in the KEV list.
No CISA SSVC assessment for this CVE yet.
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 2, 2026.
Score over time
2021–2026- EPSS v1
- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Percentile over time
- EPSS v1
- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Table of values (61 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 2, 2026 | 12.91% (0.12912) | 96.20th | v5 (v2026.06.15) |
| Jun 15, 2026 | 13.35% (0.13348) | 95.91th | v5 (v2026.06.15) |
| Mar 22, 2026 | 66.00% (0.65998) | 98.49th | v4 (v2025.03.14) |
| Mar 4, 2026 | 68.08% (0.68081) | 98.56th | v4 (v2025.03.14) |
| Mar 1, 2026 | 34.94% (0.34937) | 96.96th | v4 (v2025.03.14) |
| Feb 4, 2026 | 68.08% (0.68081) | 98.55th | v4 (v2025.03.14) |
| Feb 1, 2026 | 34.94% (0.34937) | 96.93th | v4 (v2025.03.14) |
| Jan 4, 2026 | 68.08% (0.68081) | 98.53th | v4 (v2025.03.14) |
| Jan 1, 2026 | 34.94% (0.34937) | 96.90th | v4 (v2025.03.14) |
| Dec 28, 2025 | 68.08% (0.68081) | 98.53th | v4 (v2025.03.14) |
| Dec 27, 2025 | 41.26% (0.41256) | 97.27th | v4 (v2025.03.14) |
| Dec 18, 2025 | 68.08% (0.68081) | 98.52th | v4 (v2025.03.14) |
| Dec 13, 2025 | 62.78% (0.62784) | 98.29th | v4 (v2025.03.14) |
| Dec 8, 2025 | 63.96% (0.63958) | 98.33th | v4 (v2025.03.14) |
| Dec 4, 2025 | 62.56% (0.62557) | 98.27th | v4 (v2025.03.14) |
| Dec 1, 2025 | 27.47% (0.27470) | 96.25th | v4 (v2025.03.14) |
| Nov 21, 2025 | 62.56% (0.62557) | 98.27th | v4 (v2025.03.14) |
| Nov 18, 2025 | 76.89% (0.76886) | 99.03th | v4 (v2025.03.14) |
| Nov 4, 2025 | 67.88% (0.67879) | 98.51th | v4 (v2025.03.14) |
| Nov 1, 2025 | 33.38% (0.33383) | 96.73th | v4 (v2025.03.14) |
| Oct 28, 2025 | 67.88% (0.67879) | 98.51th | v4 (v2025.03.14) |
| Oct 27, 2025 | 37.52% (0.37523) | 97.01th | v4 (v2025.03.14) |
| Oct 4, 2025 | 67.88% (0.67879) | 98.53th | v4 (v2025.03.14) |
| Oct 1, 2025 | 33.38% (0.33383) | 96.80th | v4 (v2025.03.14) |
| Sep 14, 2025 | 37.52% (0.37523) | 97.08th | v4 (v2025.03.14) |
| Sep 4, 2025 | 33.73% (0.33735) | 96.82th | v4 (v2025.03.14) |
| Sep 1, 2025 | 10.69% (0.10690) | 93.08th | v4 (v2025.03.14) |
| Aug 4, 2025 | 33.73% (0.33735) | 96.78th | v4 (v2025.03.14) |
| Aug 1, 2025 | 10.69% (0.10690) | 93.07th | v4 (v2025.03.14) |
| Jul 30, 2025 | 33.73% (0.33735) | 96.78th | v4 (v2025.03.14) |
| Jul 4, 2025 | 64.76% (0.64759) | 98.35th | v4 (v2025.03.14) |
| Jul 1, 2025 | 29.45% (0.29450) | 96.40th | v4 (v2025.03.14) |
| Jun 12, 2025 | 64.76% (0.64759) | 98.33th | v4 (v2025.03.14) |
| Jun 4, 2025 | 78.24% (0.78244) | 98.95th | v4 (v2025.03.14) |
| Jun 1, 2025 | 49.13% (0.49130) | 97.64th | v4 (v2025.03.14) |
| May 4, 2025 | 78.24% (0.78244) | 98.95th | v4 (v2025.03.14) |
| May 1, 2025 | 49.13% (0.49130) | 97.62th | v4 (v2025.03.14) |
| Apr 20, 2025 | 78.24% (0.78244) | 98.94th | v4 (v2025.03.14) |
| Apr 19, 2025 | 49.13% (0.49130) | 97.59th | v4 (v2025.03.14) |
| Apr 16, 2025 | 78.24% (0.78244) | 98.94th | v4 (v2025.03.14) |
| Apr 13, 2025 | 49.13% (0.49130) | 97.57th | v4 (v2025.03.14) |
| Mar 26, 2025 | 78.24% (0.78244) | 98.98th | v4 (v2025.03.14) |
| Mar 25, 2025 | 49.72% (0.49716) | 97.57th | v4 (v2025.03.14) |
| Mar 22, 2025 | 78.54% (0.78543) | 99.02th | v4 (v2025.03.14) |
| Mar 21, 2025 | 49.72% (0.49716) | 97.60th | v4 (v2025.03.14) |
| Mar 20, 2025 | 78.54% (0.78543) | 99.02th | v4 (v2025.03.14) |
| Mar 19, 2025 | 49.72% (0.49716) | 97.48th | v4 (v2025.03.14) |
| Mar 17, 2025 | 78.54% (0.78543) | 98.99th | v4 (v2025.03.14) |
| Jul 20, 2024 | 1.57% (0.01565) | 87.37th | v3 (v2023.03.01) |
| Sep 5, 2023 | 1.57% (0.01565) | 85.64th | v3 (v2023.03.01) |
| Jul 8, 2023 | 1.98% (0.01985) | 87.21th | v3 (v2023.03.01) |
| Jul 3, 2023 | 1.67% (0.01673) | 85.93th | v3 (v2023.03.01) |
| Mar 7, 2023 | 2.26% (0.02259) | 87.83th | v3 (v2023.03.01) |
| Mar 6, 2023 | 1.54% (0.01537) | 74.52th | v2 (v2022.01.01) |
| Feb 23, 2023 | 1.54% (0.01537) | 74.48th | v2 (v2022.01.01) |
| Apr 1, 2022 | 1.54% (0.01537) | 72.41th | v2 (v2022.01.01) |
| Feb 4, 2022 | 1.54% (0.01537) | 51.33th | v2 (v2022.01.01) |
| Feb 3, 2022 | 2.57% (0.02567) | 55.02th | v1 |
| Jan 6, 2022 | 2.57% (0.02567) | 54.58th | v1 |
| Sep 1, 2021 | 2.57% (0.02567) | 78.88th | v1 |
| Apr 14, 2021 | 2.57% (0.02567) | 0.00th | v1 |
References (13)
- http://www.squid-cache.org/Advisories/SQUID-2018_2.txt x_refsource_CONFIRMPatchVendor Advisory
- http://www.squid-cache.org/Versions/v3/3.5/changesets/SQUID-2018_2.patch x_refsource_CONFIRMPatchVendor Advisory
- http://www.squid-cache.org/Versions/v4/changesets/SQUID-2018_2.patch x_refsource_CONFIRMPatchVendor Advisory
- https://access.redhat.com/security/cve/CVE-2018-1000027 Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1536942 Issue Tracking
- https://github.com/squid-cache/squid/pull/129/files x_refsource_CONFIRMThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2018/02/msg00001.html mailing-listx_refsource_MLISTMailing ListThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2018/02/msg00002.html mailing-listx_refsource_MLISTMailing ListThird Party Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2018-1000027
- https://usn.ubuntu.com/3557-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://usn.ubuntu.com/4059-2/ vendor-advisoryx_refsource_UBUNTU
- https://www.cve.org/CVERecord?id=CVE-2018-1000027
- https://www.debian.org/security/2018/dsa-4122 vendor-advisoryx_refsource_DEBIANThird Party Advisory
Change history (0)
No recorded changes yet.