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No exploitation reportedFix available

CVE-2021-33574

No exploitation reported by the sources we read.

  • Published2021-05-25
  • WeaknessCWE-416

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

The mq_notify function in the GNU C Library (aka glibc) versions 2.32 and 2.33 has a use-after-free. It may use the notification thread attributes object (passed through its struct sigevent parameter) after it has been freed by the caller, leading to a denial of service (application crash) or possibly unspecified other impact.

Timeline

dates in UTC
  1. 2021-05-2522:15CVE publishedNVD

Versions per branch

NVD
Fedoraproject fedora
BranchAffectedFixed in
33.x= 33no fix published
34.x= 34no fix published
Gnu glibc
BranchAffectedFixed in
2.32= 2.32no fix published
2.33= 2.33no fix published
Debian debian linux
BranchAffectedFixed in
10.0= 10.0no fix published

10 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • eglibcUbuntu:Pro:14.04:LTSall versions · no fixed version listed
  • glibcUbuntu:Pro:20.04:LTSall versions · no fixed version listed
  • glibcUbuntu:Pro:18.04:LTSall versions · no fixed version listed
  • glibcUbuntu:Pro:16.04:LTSall versions · no fixed version listed
  • glibcTuxCare:OracleLinux:6all versions · fixed in 2.12-2.213.el6.cloudlinux.elsand 6 other packages
  • glibcTuxCare:CentOS:8.4all versions · fixed in 2.28-151.el8.4.tuxcare.els1and 211 other packages
  • glibcTuxCare:CentOS:6all versions · fixed in 2.12-2.213.el6.cloudlinux.elsand 6 other packages
  • glibcSUSE:OpenStack Cloud Crowbar 9all versions · fixed in 2.22-114.15.1

46 more package ranges on OSV.dev

Vendor advisories

  • CVE-2021-33574 Red Hat Product Security882 products fixed · 21 known affected

    glibc: mq_notify does not handle separately allocated thread attributes

    compat-glibc-headers as a component of Red Hat Enterprise Linux 6 · compat-glibc.src as a component of Red Hat Enterprise Linux 6 · glibc as a component of Red Hat Enterprise Linux 6 · +18 more

  • ICSA-23-348-10 CISA5 known affected

    Siemens SIMATIC S7-1500

    SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) · +2 more

  • SSA-398330 Siemens ProductCERT5 known affected

    SSA-398330: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP >= V3.1.0 and < V3.1.5

    SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= V3.1.0 < V3.1.5 · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= V3.1.0 < V3.1.5 · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= V3.1.0 < V3.1.5 · +2 more

  • ICSA-23-166-10 CISA1 known affected

    Siemens SIMATIC S7-1500 TM MFP BIOS

    SIMATIC S7-1500 TM MFP - BIOS

  • SSA-831302 Siemens ProductCERT1 known affected

    SSA-831302: Vulnerabilities in the BIOS of the SIMATIC S7-1500 TM MFP before V1.3.0

    SIMATIC S7-1500 TM MFP - BIOS

  • RHSA-2021:4358 Red Hat Product Security882 products fixed

    Red Hat Security Advisory: glibc security, bug fix, and enhancement update

Full record on NVD

Fix

  1. Vendor fix CISA ICSA-23-348-10 · 5 productsUpdate to V3.1.5 or later version
  2. Vendor fix Siemens ProductCERT SSA-398330 · 1 productUpdate to V3.1.5 or later version
  3. Vendor fix Siemens ProductCERT SSA-831302 · 1 productUpdate to V1.3.0 or later version
  4. Vendor fix CISA ICSA-23-166-10 · 1 productUpdate to V1.3.0 or later version
  5. Vendor fix Red Hat Product Security RHSA-2021:4358 · 882 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 For the update to take effect, all services linked to the glibc library must be restarted, or the system rebooted.
  6. Workaround from the vendor Siemens ProductCERT SSA-831302 · 1 productOnly build and run applications from trusted sources

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2021-05-25
Last Modified
2026-10-14
NVD status
Modified
GitHub Advisory
GHSA-rx5m-j84j-22pg

Frequently asked questions

What is CVE-2021-33574?

The mq_notify function in the GNU C Library (aka glibc) versions 2.32 and 2.33 has a use-after-free. It may use the notification thread attributes object (passed through its struct sigevent parameter) after it has been freed by the caller, leading to a denial of service (application crash) or possibly unspecified other impact.

Is CVE-2021-33574 actively exploited?

Active exploitation of CVE-2021-33574 has not been confirmed. Its EPSS score was 3.5% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-33574?

CVE-2021-33574 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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