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 misbeh
Noroxi assessment
Priority: Monitor (action score 36/100)
- Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
- Probability of exploitation in the next 30 days: 4.6% (FIRST EPSS); higher than 91.8% of all records.
- 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.
- Fixed version: expat (AlmaLinux:8) 2.2.5-8.el8_6.2; expat-devel (AlmaLinux:8) 2.2.5-8.el8_6.2; expat (Alpine:v3.12) 2.2.10-r0.
- Mentioned 2 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Low priority for now. Upgrade to expat (AlmaLinux:8) 2.2.5-8.el8_6.2; expat-devel (AlmaLinux:8) 2.2.5-8.el8_6.2; expat (Alpine:v3.12) 2.2.10-r0 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
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).
- Published
- Jan 1, 2022
- Updated
- Oct 14, 2026
- EPSS
- 4.6% · 91th percentile
- CWE
- CWE-682
Report tools
Action score
36
Monitor
Low priority for now.
- CVSS
- 35 / 40 · 8.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 1 / 30 · 4.6%
CISA SSVC decision
- Exploitation
- proof of concept
- Automatable
- no
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 8.8
- CNA · mitre
- 8.8
- agree
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- Proof of concept exists, no weaponized module
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| libexpat project | libexpat | cpe:2.3:a:libexpat_project:libexpat |
| tenable | nessus | cpe:2.3:a:tenable:nessus |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
| siemens | sinema remote connect server | cpe:2.3:a:siemens:sinema_remote_connect_server |
| netapp | active iq unified manager | cpe:2.3:a:netapp:active_iq_unified_manager |
| netapp | hci baseboard management controller | cpe:2.3:a:netapp:hci_baseboard_management_controller |
| netapp | oncommand workflow automation | cpe:2.3:a:netapp:oncommand_workflow_automation |
| netapp | solidfire & hci management node | cpe:2.3:a:netapp:solidfire_&_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.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:8 | expat | before 2.2.5-8.el8_6.2 | 2.2.5-8.el8_6.2 |
| AlmaLinux:8 | expat-devel | before 2.2.5-8.el8_6.2 | 2.2.5-8.el8_6.2 |
| Alpine:v3.12 | expat | before 2.2.10-r0 | 2.2.10-r0 |
| Alpine:v3.13 | expat | before 2.2.10-r2 | 2.2.10-r2 |
| Alpine:v3.14 | expat | before 2.4.3-r0 | 2.4.3-r0 |
| Debian:10 | expat | before 2.2.6-2+deb10u2 | 2.2.6-2+deb10u2 |
| Debian:11 | expat | before 2.2.10-2+deb11u1 | 2.2.10-2+deb11u1 |
| Debian:12 | expat | before 2.4.3-1 | 2.4.3-1 |
| Debian:12 | libxmltok | from 0 | — |
| Debian:9 | expat | before 2.2.0-2+deb9u4 | 2.2.0-2+deb9u4 |
| openSUSE:Leap 15.3 | expat | before 2.2.5-3.9.1 | 2.2.5-3.9.1 |
| openSUSE:Tumbleweed | expat | before 2.4.3-1.1 | 2.4.3-1.1 |
| Red Hat:enterprise_linux:7::client | expat | before 0:2.1.0-14.el7_9 | 0:2.1.0-14.el7_9 |
| Red Hat:enterprise_linux:7::client | expat-debuginfo | before 0:2.1.0-14.el7_9 | 0:2.1.0-14.el7_9 |
| Red Hat:enterprise_linux:7::client | expat-devel | before 0:2.1.0-14.el7_9 | 0:2.1.0-14.el7_9 |
| Red Hat:enterprise_linux:7::client | expat-static | before 0:2.1.0-14.el7_9 | 0:2.1.0-14.el7_9 |
| Red Hat:enterprise_linux:8::baseos | expat | before 0:2.2.5-4.el8_5.3 | 0:2.2.5-4.el8_5.3 |
| Red Hat:enterprise_linux:8::baseos | expat-debuginfo | before 0:2.2.5-4.el8_5.3 | 0:2.2.5-4.el8_5.3 |
| Red Hat:enterprise_linux:8::baseos | expat-debugsource | before 0:2.2.5-4.el8_5.3 | 0:2.2.5-4.el8_5.3 |
| Red Hat:enterprise_linux:8::baseos | expat-devel | before 0:2.2.5-4.el8_5.3 | 0:2.2.5-4.el8_5.3 |
| Red Hat:rhel_aus:8.2::baseos | expat | before 0:2.2.10-1.el8_2 | 0:2.2.10-1.el8_2 |
| Red Hat:rhel_aus:8.4::baseos | expat | before 0:2.2.10-1.el8_4 | 0:2.2.10-1.el8_4 |
| Rocky Linux:8 | expat | before 0:2.2.5-4.el8_5.3 | 0:2.2.5-4.el8_5.3 |
| SUSE:HPE Helion OpenStack 8 | expat | before 2.1.0-21.12.1 | 2.1.0-21.12.1 |
+2
Same product
libexpat project: all recordsOther 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-2022-23852Expat (aka libexpat) before 2.4.4 has a signed integer overflow in XML_GetBuffer, for configurations with a nonzero XML_CONTEXT_BYTES.41Plan
- CVE-2022-22822addBinding in xmlparse.c in Expat (aka libexpat) before 2.4.3 has an integer overflow.41Plan
Published before and after this one in the same product
- ← EarlierCVE-2018-20843Jun 24, 2019 · In libexpat in Expat before 2.2.7, XML input including XML names that contain a large number of colons could make the XML parser consume a h32Monitor
- ← EarlierCVE-2019-15903Sep 4, 2019 · In libexpat before 2.2.8, crafted XML input could fool the parser into changing from DTD parsing to document parsing too early; a consecutiv32Monitor
- Later →CVE-2021-46143Jan 6, 2022 · In doProlog in xmlparse.c in Expat (aka libexpat) before 2.4.3, an integer overflow exists for m_groupSize.32Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| almalinux:expat | 2.2.5-8.el8_6.2 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:expat-devel | 2.2.5-8.el8_6.2 · AlmaLinux:8 | Package registry (OSV) |
| alpine:expat | 2.2.10-r0 · Alpine:v3.12 | Package registry (OSV) |
| debian:expat | 2.4.3-1 · Debian:12 | Package registry (OSV) |
| opensuse:expat | 2.2.5-3.9.1 · openSUSE:Leap 15.3 | Package registry (OSV) |
| red hat:expat | 0:2.2.5-4.el8_5.3 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:expat-debuginfo | 0:2.2.5-4.el8_5.3 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:expat-debugsource | 0:2.2.5-4.el8_5.3 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:expat-devel | 0:2.2.5-4.el8_5.3 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:expat-static | 0:2.1.0-14.el7_9 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| rocky linux:expat | 0:2.2.5-4.el8_5.3 · Rocky Linux:8 | Package registry (OSV) |
| suse:expat | 2.2.5-3.9.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP3 | Package 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.
| Source | Kind | Date |
|---|---|---|
| Proof-of-concept repository on GitHub | stars:0 | 2022-04-11 |
| Proof-of-concept repository on GitHub | stars:0 | 2022-05-25 |
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.
- Published
- First PoC+99 d
- TodayNov 6, 2026+1770 d
No history yet (it accumulates with the daily EPSS job).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, 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.
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-22-0258 · Mar 29, 2022(RedHat Güvenlik Güncellemesi)
- TR-22-0247 · Mar 24, 2022(RedHat Güvenlik Güncellemesi)
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
Weakness class (CWE)
CWE-682 · Incorrect CalculationCVSS 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.
Attack patterns (CAPEC)
ATT&CK techniques
—
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (8 more)Show less
- cert-portal.siemens.com/productcert/pdf/ssa-484086.pdf
- github.com/libexpat/libexpat/pull/534
- security.gentoo.org/glsa/202209-24
- security.netapp.com/advisory/ntap-20220121-0004/
- www.debian.org/security/2022/dsa-5073
- www.tenable.com/security/tns-2022-05
- cert-portal.siemens.com/productcert/html/ssa-398330.html
- cert-portal.siemens.com/productcert/html/ssa-484086.html
Vendor advisories and official records. Exploit/PoC links are deliberately left out.