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Fencer Vulns
high 7.7

CVE-2023-27538 json

An authentication bypass vulnerability exists in libcurl prior to v8.0.0 where it reuses a...

published 2023-03-30 3 y ago modified 2026-10-14 25 d ago also EUVD-2023-31293 , JLSEC-2025-33

cvss
7.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.5%
EPSS 1.5% chance of exploitation in 30 days, percentile 73%
public exploits
0
none known

Summary

An authentication bypass vulnerability exists in libcurl prior to v8.0.0 where it reuses a previously established SSH connection despite the fact that an SSH option was modified, which should have prevented reuse. libcurl maintains a pool of previously used connections to reuse them for subsequent transfers if the configurations match. However, two SSH settings were omitted from the configuration check, allowing them to match easily, potentially leading to the reuse of an inappropriate connection.

Patch / fix

  • julia CURL_jll 8.5.0+0
  • julia LibCURL_jll 8.0.1+0
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • curl Debian 14, Debian 13, Debian 12 7.88.1-7

debian advisories DEBIAN-CVE-2023-27538

  • curl Ubuntu 18.04 LTS 7.58.0-2ubuntu3.24
  • curl Ubuntu 20.04 LTS 7.68.0-1ubuntu2.18
  • curl Ubuntu 22.04 LTS 7.81.0-1ubuntu1.10

ubuntu advisories UBUNTU-CVE-2023-27538

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

  • curl RHEL 9 7.76.1-26.el9
  • libcurl RHEL 9 7.76.1-26.el9
  • curl-minimal RHEL 9 7.76.1-26.el9
  • libcurl-minimal RHEL 9 7.76.1-26.el9

red hat advisories RHSA-2023:6679

  • curl SLES for SAP 12 SP4, SLES 12 SP4-LTSS, SLES 12 SP4-ESPOS +2 more 7.60.0-4.56.1
  • curl SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLE High Performance Computing 15 SP1-LTSS +1 more 7.60.0-150000.51.1
  • curl SLE Real Time 15 SP3, SLE Micro 5.2, SLE Micro 5.1 7.66.0-150200.4.52.1
  • curl SLE Module for Basesystem 15 SP4, SLE Micro 5.3, openSUSE Leap Micro 5.3 +1 more 7.79.1-150400.5.18.1
  • curl SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 7.60.0-11.60.1

suse advisories SUSE-SU-2023:2228-1SUSE-SU-2023:2226-1SUSE-SU-2023:1711-1SUSE-SU-2023:1582-1SUSE-SU-2023:0865-1

  • curl openSUSE Tumbleweed 8.0.1-1.1

opensuse advisories openSUSE-SU-2024:12812-1

  • curl AlmaLinux 9 7.76.1-26.el9
  • libcurl AlmaLinux 9 7.76.1-26.el9
  • curl-minimal AlmaLinux 9 7.76.1-26.el9
  • libcurl-minimal AlmaLinux 9 7.76.1-26.el9

almalinux advisories ALSA-2023:6679

  • curl Alpine 3.16, Alpine 3.15, Alpine 3.14 8.0.1-r0
  • curl Alpine 3.17 7.88.1-r1
  • curl Alpine 3.24, Alpine 3.23, Alpine 3.22 +4 more 8.0.0-r0

alpine advisories ALPINE-CVE-2023-27538

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • cmake CBL-Mariner 2.0 3.21.4-13
  • mysql CBL-Mariner 2.0 8.0.34-1
  • rust CBL-Mariner 2.0 1.72.0-2
  • curl CBL-Mariner 2.0 8.0.1-1
  • cmake Azure Linux 3.0 3.28.2-1
  • tensorflow Azure Linux 3.0 2.16.1-1

azure linux advisories AZL-25786AZL-25803AZL-25808AZL-25848AZL-34613AZL-38257

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2023-27538 updated cvss 5.5

curl: SSH connection too eager reuse still

  • Red Hat .NET Core 3.1 on Red Hat Enterprise Linux rh-dotnet31-curl, rh-dotnet31-libcurl Red Hat Enterprise Linux 6 curl, libcurl
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 curl, libcurl
    affected: no fix planned “Will not fix”
  • Red Hat JBCS httpd 2.4.51.sp2
    fixed: vendor fix RHSA-2023:3355
  • Red Hat Enterprise Linux AppStream (v. 9) libcurl-devel 7.76.1-26.el9, curl-debuginfo 7.76.1-26.el9, curl-debugsource 7.76.1-26.el9, libcurl-debuginfo 7.76.1-26.el9, curl-minimal-debuginfo 7.76.1-26.el9, libcurl-minimal-debuginfo 7.76.1-26.el9 Red Hat Enterprise Linux BaseOS (v. 9) curl 7.76.1-26.el9, libcurl 7.76.1-26.el9, curl-minimal 7.76.1-26.el9, libcurl-minimal 7.76.1-26.el9
    fixed: vendor fix RHSA-2023:6679
  • Red Hat Enterprise Linux 8 curl, libcurl, libcurl-minimal
    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

cisa ICSA-23-348-10 updated cvss 7.5

Siemens SIMATIC S7-1500

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.0, < 3.1.5
    affected: fixed in V3.1.5, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
17 mo ago

Exploit prediction

1.45% chance of exploitation in the next 30 days, higher than 73% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • hackerone.com https://hackerone.com/reports/1898475 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.7 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
CNA 3.1 7.7 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
OSV 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
julia CURL_jll
<8.5.0+0
8.5.0+0
julia LibCURL_jll
<8.0.1+0
8.0.1+0

Affected products

  • n/a https://github.com/curl/curl
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

Classification

Weakness
  • CWE-305 Authentication Bypass by Primary Weakness
  • CWE-287 Improper Authentication

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.