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Fencer Vulns
medium 5.9

CVE-2023-27371 json

GNU libmicrohttpd before 0.9.76 allows remote DoS (Denial of Service) due to improper parsing of a multipart/form-data boundary in the post…

published 2023-02-28 3 y ago modified 2026-10-14 25 d ago also EUVD-2023-31147

cvss
5.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.3%
EPSS 1.3% chance of exploitation in 30 days, percentile 69%
public exploits
0
none known

Summary

GNU libmicrohttpd before 0.9.76 allows remote DoS (Denial of Service) due to improper parsing of a multipart/form-data boundary in the postprocessor.c MHD_create_post_processor() method. This allows an attacker to remotely send a malicious HTTP POST packet that includes one or more '\0' bytes in a multipart/form-data boundary field, which - assuming a specific heap layout - will result in an out-of-bounds read and a crash in the find_boundary() function.

Patch / fix

  • 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
  • libmicrohttpd Debian 14, Debian 13, Debian 12 0.9.75-6

debian advisories DEBIAN-CVE-2023-27371

  • libmicrohttpd RHEL 8 1:0.9.59-3.el8
  • libmicrohttpd RHEL 9 1:0.9.72-5.el9
  • libmicrohttpd RHEL 8.6 EUS 1:0.9.59-2.el8_6.1
  • libmicrohttpd RHEL 8.8 EUS 1:0.9.59-2.el8_8.1

red hat advisories RHSA-2024:1109RHSA-2024:0584RHSA-2023:7090RHSA-2023:6566

  • libmicrohttpd SLE Real Time 15 SP3, SLE Module for Desktop Applications 15 SP4, SLE Module for Basesystem 15 SP4 +6 more 0.9.57-150000.3.3.1
  • libmicrohttpd SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 0.9.30-6.3.1

suse advisories SUSE-SU-2023:1686-2SUSE-SU-2023:1944-1SUSE-SU-2023:1686-1

  • libmicrohttpd AlmaLinux 8 1:0.9.59-3.el8
  • libmicrohttpd AlmaLinux 9 1:0.9.72-5.el9

almalinux advisories ALSA-2023:7090ALSA-2023:6566

  • libmicrohttpd Rocky Linux 9 1:0.9.72-5.el9
  • libmicrohttpd Rocky Linux 8 1:0.9.59-3.el8

rocky linux advisories RLSA-2023:6566RLSA-2023:7090

  • libmicrohttpd CBL-Mariner 2.0 0.9.76-1

azure linux advisories AZL-25347

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-2023-27371 updated cvss 5.9

libmicrohttpd: remote DoS

  • Red Hat Enterprise Linux 6 libmicrohttpd Red Hat Enterprise Linux 7 libmicrohttpd
    affected: no fix planned “Out of support scope”
  • Red Hat CodeReady Linux Builder (v. 8) libmicrohttpd-doc 0.9.59-3.el8, libmicrohttpd-devel 0.9.59-3.el8, libmicrohttpd-debuginfo 0.9.59-3.el8, libmicrohttpd-debugsource 0.9.59-3.el8
    fixed: vendor fix RHSA-2023:7090
  • Red Hat CodeReady Linux Builder (v. 9) libmicrohttpd-doc 0.9.72-5.el9, libmicrohttpd-devel 0.9.72-5.el9, libmicrohttpd-debuginfo 0.9.72-5.el9, libmicrohttpd-debugsource 0.9.72-5.el9
    fixed: vendor fix RHSA-2023:6566
  • Red Hat CodeReady Linux Builder EUS (v.8.6) libmicrohttpd-doc 0.9.59-2.el8_6.1, libmicrohttpd-devel 0.9.59-2.el8_6.1, libmicrohttpd-debuginfo 0.9.59-2.el8_6.1, libmicrohttpd-debugsource 0.9.59-2.el8_6.1
    fixed: vendor fix RHSA-2024:1109
  • Red Hat CodeReady Linux Builder EUS (v.8.8) libmicrohttpd-doc 0.9.59-2.el8_8.1, libmicrohttpd-devel 0.9.59-2.el8_8.1, libmicrohttpd-debuginfo 0.9.59-2.el8_8.1, libmicrohttpd-debugsource 0.9.59-2.el8_8.1
    fixed: vendor fix RHSA-2024:0584
  • Red Hat Enterprise Linux AppStream (v. 9) libmicrohttpd 0.9.72-5.el9
    fixed: vendor fix RHSA-2023:6566
  • Red Hat Enterprise Linux BaseOS (v. 8) libmicrohttpd 0.9.59-3.el8
    fixed: vendor fix RHSA-2023:7090
  • Red Hat Enterprise Linux BaseOS EUS (v.8.6) libmicrohttpd 0.9.59-2.el8_6.1
    fixed: vendor fix RHSA-2024:1109
show 1 more
  • Red Hat Enterprise Linux BaseOS EUS (v.8.8) libmicrohttpd 0.9.59-2.el8_8.1
    fixed: vendor fix RHSA-2024:0584

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 5.9

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
19 mo ago

Exploit prediction

1.25% chance of exploitation in the next 30 days, higher than 69% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/0xhebi/CVEs/tree/main/GNU%20Libmicrohttpd referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.9 CVSS:3.1/AC:H/AV:N/A:H/C:N/I:N/PR:N/S:U/UI:N
CNA 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • 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

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.