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CVE-2023-39976

27
FAUCET Score

CVE-2023-39976 is a critical buffer overflow vulnerability affecting libqb versions prior to 2.0.8, specifically within the log_blackbox.c component. This flaw, stemming from inadequate header size consideration for long log messages, carries a CVSS score of 9.8 (CRITICAL), indicating it can be exploited remotely without authentication or user interaction to achieve full confidentiality, integrity, and availability compromise. While no active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion has been observed, its high severity warrants immediate patching for affected ClusterLabs libqb deployments.

Impacted Technologies

VendorProductVersion(s)CPE
< 2.0.8CPE matchmatch criteria
cpe:2.3:a:clusterlabs:libqb:*:*:*:*:*:*:*:*

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
0.98%
Probability of exploitation in next 30 days
EPSS Percentile
58.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0098 is in the 44th 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 (6)

github_advisorypatch availablevia nvd_reference
View patch
microsoftpatch availablevia msrc
Product: azl3 libqb 2.0.8-1 on Azure Linux 3.0Fixed in: 2.0.8-1
microsoftpatch availablevia msrc
Product: 18416-17084Fixed in: 2.0.8-1
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: libqb-0:2.0.6-4.el9_3
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.0 Extended Update SupportFixed in: libqb-0:2.0.3-12.el9_0
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.2 Extended Update SupportFixed in: libqb-0:2.0.6-3.el9_2
View patch

Vendor Advisories (2)

microsoft2023-Aug/CVE-2023-39976Critical

log_blackbox.c in libqb before 2.0.8 allows a buffer overflow via long log messages because the header size is not considered.

Aug 8, 2023
redhatCVE-2023-39976Moderate

libqb: Buffer overflow in log_blackbox.c

Aug 8, 2023

References

github.com / ClusterLabs/libqb/commit/1bbaa929b77113532785c408dd1b41cd0521ffc8
Patch
github.com / ClusterLabs/libqb/compare/v2.0.7...v2.0.8
Not Applicable
github.com / ClusterLabs/libqb/pull/490
Patch
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/KECNF7LFBPE57XSBT6EM7ACVMIBP63WH