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CVE-2021-45960· NVD / CVE Program· CNA mitre

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 misbeh

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 memory).

HighCVSS 8.8 · v3.1—Proof of concept Fix available

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Published
Jan 1, 2022
Updated
Jun 17, 2026
EPSS
4.2% · 91th percentile
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Report tools

JSON

Action score

36

Monitor

Low priority for now.

CVSS
35 / 40 · 8.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 4.2%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

Affected systems

VendorProduct
libexpat projectlibexpat
tenablenessus
debiandebian linux
siemenssinema remote connect server
netappactive iq unified manager
netapphci baseboard management controller
netapponcommand workflow automation
netappsolidfire \& hci management node

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux10.0
  • debian debian linux11.0
  • libexpat project libexpatbefore 2.4.3
  • netapp active iq unified managerall versions
  • netapp hci baseboard management controllerh610c
  • netapp hci baseboard management controllerh610s
  • netapp hci baseboard management controllerh615c
  • netapp oncommand workflow automationall versions
  • netapp solidfire & hci management nodeall versions
  • siemens sinema remote connect serverbefore 3.1
  • tenable nessusbefore 8.15.3
  • tenable nessus10.0.0 and later · before 10.1.1

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8expatbefore 2.2.5-8.el8_6.22.2.5-8.el8_6.2
AlmaLinux:8expat-develbefore 2.2.5-8.el8_6.22.2.5-8.el8_6.2
Alpine:v3.12expatbefore 2.2.10-r02.2.10-r0
Alpine:v3.13expatbefore 2.2.10-r22.2.10-r2
Alpine:v3.14expatbefore 2.4.3-r02.4.3-r0
Debian:10expatbefore 2.2.6-2+deb10u22.2.6-2+deb10u2
Debian:11expatbefore 2.2.10-2+deb11u12.2.10-2+deb11u1
Debian:12expatbefore 2.4.3-12.4.3-1
Debian:12libxmltokall versions—
Debian:9expatbefore 2.2.0-2+deb9u42.2.0-2+deb9u4
openSUSE:Leap 15.3expatbefore 2.2.5-3.9.12.2.5-3.9.1
openSUSE:Tumbleweedexpatbefore 2.4.3-1.12.4.3-1.1
Red Hat:enterprise_linux:7::clientexpatbefore 0:2.1.0-14.el7_90:2.1.0-14.el7_9
Red Hat:enterprise_linux:7::clientexpat-debuginfobefore 0:2.1.0-14.el7_90:2.1.0-14.el7_9
Red Hat:enterprise_linux:7::clientexpat-develbefore 0:2.1.0-14.el7_90:2.1.0-14.el7_9
Red Hat:enterprise_linux:7::clientexpat-staticbefore 0:2.1.0-14.el7_90:2.1.0-14.el7_9
Red Hat:enterprise_linux:8::baseosexpatbefore 0:2.2.5-4.el8_5.30:2.2.5-4.el8_5.3
Red Hat:enterprise_linux:8::baseosexpat-debuginfobefore 0:2.2.5-4.el8_5.30:2.2.5-4.el8_5.3
Red Hat:enterprise_linux:8::baseosexpat-debugsourcebefore 0:2.2.5-4.el8_5.30:2.2.5-4.el8_5.3
Red Hat:enterprise_linux:8::baseosexpat-develbefore 0:2.2.5-4.el8_5.30:2.2.5-4.el8_5.3
Red Hat:rhel_aus:8.2::baseosexpatbefore 0:2.2.10-1.el8_20:2.2.10-1.el8_2
Red Hat:rhel_aus:8.4::baseosexpatbefore 0:2.2.10-1.el8_40:2.2.10-1.el8_4
Rocky Linux:8expatbefore 0:2.2.5-4.el8_5.30:2.2.5-4.el8_5.3
SUSE:HPE Helion OpenStack 8expatbefore 2.1.0-21.12.12.1.0-21.12.1

+2

Other highest-scoring records for the same primary product.

  • CVE-2022-25236xmlparse.c in Expat (aka libexpat) before 2.4.5 allows attackers to insert namespace-separator characters into namespace URIs.
    50Plan
  • CVE-2022-25315In Expat (aka libexpat) before 2.4.5, there is an integer overflow in storeRawNames.
    40Plan
  • CVE-2022-25235xmltok_impl.c in Expat (aka libexpat) before 2.4.5 lacks certain validation of encoding, such as checks for whether a UTF-8 character is val
    40Plan
  • CVE-2022-23852Expat (aka libexpat) before 2.4.4 has a signed integer overflow in XML_GetBuffer, for configurations with a nonzero XML_CONTEXT_BYTES.
    40Plan
  • CVE-2022-22824defineAttribute in xmlparse.c in Expat (aka libexpat) before 2.4.3 has an integer overflow.
    40Plan
  • CVE-2022-22823build_model in xmlparse.c in Expat (aka libexpat) before 2.4.3 has an integer overflow.
    40Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:expat2.2.5-8.el8_6.2 · AlmaLinux:8Package registry (OSV)
almalinux:expat-devel2.2.5-8.el8_6.2 · AlmaLinux:8Package registry (OSV)
alpine:expat2.2.10-r0 · Alpine:v3.12Package registry (OSV)
debian:expat2.4.3-1 · Debian:12Package registry (OSV)
opensuse:expat2.2.5-3.9.1 · openSUSE:Leap 15.3Package registry (OSV)
red hat:expat0:2.2.5-4.el8_5.3 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:expat-debuginfo0:2.2.5-4.el8_5.3 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:expat-debugsource0:2.2.5-4.el8_5.3 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:expat-devel0:2.2.5-4.el8_5.3 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:expat-static0:2.1.0-14.el7_9 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
rocky linux:expat0:2.2.5-4.el8_5.3 · Rocky Linux:8Package registry (OSV)
suse:expat2.2.5-3.9.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP3Package registry (OSV)

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Proof-of-concept repository on GitHub ×2

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHubstars:02022-04-11
Proof-of-concept repository on GitHubstars:02022-05-25

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. First PoC+99 d
  3. TodaySep 30, 2026+1733 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

All records