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CVE-2021-33574

32
FAUCET Score

CVE-2021-33574 is a critical use-after-free vulnerability in the mq_notify function of the GNU C Library (glibc) versions 2.32 and 2.33, affecting products like Debian and Fedora. With a CVSS score of 9.8, it presents a severe risk due to its network-based attack vector, low complexity, and potential for denial of service or other unspecified impacts. Despite its high severity, there is currently no evidence of active exploitation, publicly available exploit code, or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
2.32CPE matchmatch criteria
cpe:2.3:a:gnu:glibc:2.32:*:*:*:*:*:*:*
2.33CPE matchmatch criteria
cpe:2.3:a:gnu:glibc:2.33:*:*:*:*:*:*:*
33CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
34CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
Range not provided by sourceCPE matchmatch criteria
cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.90%
Probability of exploitation in next 30 days
EPSS Percentile
85.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0290 is in the 76th percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

microsoftpatch availablevia msrc
Product: 19006-16820Fixed in: 2.28-20
microsoftpatch availablevia msrc
Product: cm1 glibc 2.28-20 on CBL Mariner 1.0Fixed in: 2.28-20
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: glibc-0:2.28-164.el8
View patch

Vendor Advisories (2)

redhatCVE-2021-33574Low

glibc: mq_notify does not handle separately allocated thread attributes

May 21, 2021
microsoft2021-May/CVE-2021-33574Critical

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.

May 11, 2021

References

lists.debian.org / debian-lts-announce/2022/10/msg00021.html
Mailing ListThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/KJYYIMDDYOHTP2PORLABTOHYQYYREZDD
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/RBUUWUGXVILQXVWEOU7N42ICHPJNAEUP
security.gentoo.org / glsa/202107-07
Third Party Advisory
security.netapp.com / advisory/ntap-20210629-0005
Third Party Advisory
sourceware.org / bugzilla/show_bug.cgi
ExploitIssue TrackingThird Party Advisory
sourceware.org / bugzilla/show_bug.cgi
Issue Tracking