01 Record

CVE-2021-45960

In Expat (aka libexpat) before 2.4.3, a left shift by 29 (or more) places in the storeAtts function in xmlparse.c can lead to realloc misbehavior (e.g., allocating too few bytes, or only freeing

HighPUBLISHEDCNA: mitre

CNA base score8.8 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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02 Description

In Expat (aka libexpat) before 2.4.3, a left shift by 29 (or more) places in the storeAtts function in xmlparse.c can lead to realloc misbehavior (e.g., allocating too few bytes, or only freeing

03 Exploitation and scoring

Exploitation

Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.

SSVC decision

ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

4.67% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 91.7% of scored records. A rank, not a probability.

NVD base score

8.8 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

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

NVD analysis status

Modified. NVD last modified this record on 2026-10-14.

Red Hat severity

Moderate. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published

2022-01-01 18:47Z4 YR AGO

Last updated

2026-10-14 12:03Z15 DAYS AGO

Reserved

2022-01-01

Assigning CNA

mitre

Record state

PUBLISHED

Severity

High (CVSS 8.8)

CNA CVSS vector

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

Weaknesses

CWE-682Incorrect CalculationPillar
CWE-1335Incorrect Bitwise Shift of IntegerBase

Data version

5.2

Document digest

b1c8e459330dec4cc73b03da95ec168a166fc60537e5824445aea6666b4a97bb

05 Affected products

VendorProductVersionsPlatforms

debiandebian_linuxNot specified—

libexpat_projectlibexpatNot specified—

netappactive_iq_unified_managerNot specified—

netapphci_baseboard_management_controllerNot specified—

netapponcommand_workflow_automationNot specified—

netappsolidfire_&_hci_management_nodeNot specified—

redhatenterprise_linuxNot specified—

redhatjboss_core_servicesNot specified—

redhatrhel_ausNot specified—

redhatrhel_eus_long_lifeNot specified—

siemenssinema_remote_connect_serverNot specified—

tenablenessusNot specified—

06 References

github.comhttps://github.com/libexpat/libexpat/issues/531x_refsource_MISC
github.comhttps://github.com/libexpat/libexpat/pull/534x_refsource_MISC
bugzilla.mozilla.orghttps://bugzilla.mozilla.org/show_bug.cgi?id=1217609x_refsource_MISC
www.openwall.com[oss-security] 20220117 Expat 2.4.3 released, includes 8 security fixeshttp://www.openwall.com/lists/oss-security/2022/01/17/3mailing-listx_refsource_MLIST
security.netapp.comhttps://security.netapp.com/advisory/ntap-20220121-0004/x_refsource_CONFIRM
www.tenable.comhttps://www.tenable.com/security/tns-2022-05x_refsource_CONFIRM
www.debian.orgDSA-5073https://www.debian.org/security/2022/dsa-5073vendor-advisoryx_refsource_DEBIAN
cert-portal.siemens.comhttps://cert-portal.siemens.com/productcert/pdf/ssa-484086.pdfx_refsource_CONFIRM
security.gentoo.orgGLSA-202209-24https://security.gentoo.org/glsa/202209-24vendor-advisoryx_refsource_GENTOO
cert-portal.siemens.comhttps://cert-portal.siemens.com/productcert/html/ssa-484086.html
cert-portal.siemens.comhttps://cert-portal.siemens.com/productcert/html/ssa-398330.html

07 Fixed in

AlmaLinux 8

expat
Fixed in 2.2.5-8.el8_6.2
expat-devel
Fixed in 2.2.5-8.el8_6.2

CloudLinux 8

expat
Fixed in 2.2.5-8.el8_6.2
expat-devel
Fixed in 2.2.5-8.el8_6.2

Derived from AlmaLinux 8. Partial coverage: only packages taken from AlmaLinux 8 are listed.

Debian 12

expat
Fixed in 2.4.3-1
libxmltok
No fix yet

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 13

expat
Fixed in 2.4.3-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 14

expat
Fixed in 2.4.3-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.