CVE-2021-45960

Exp

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: 2022-01-01 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-45960 is rated High Exploit Risk (85.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 4.20%). 2 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +3.88% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-45960

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-45960

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.32% 4.20% +3.88%
2 2025-12-26 0.40% 0.32% -0.08%
3 2025-12-07 — 0.40% —

Full EPSS history (30 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-45960

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 134c704f-9b21-4f2e-91b3-4a467353bcc0
9.0 2.0 HIGH
AV:N/AC:L/Au:S/C:C/I:C/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 8.0 10.0 [email protected]

Weakness enumeration for CVE-2021-45960

OS Trackers for CVE-2021-45960

vendor priority summary link
alpine — CVE-2021-45960: 1 source package rows (expat); 8 state rows across 8 repos (3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 8, open 0. https://security.alpinelinux.org/vuln/CVE-2021-45960
debian not yet assigned CVE-2021-45960 not yet assigned priority: Debian including 2 source packages (expat, libxmltok), 7 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5, open 2. https://security-tracker.debian.org/tracker/CVE-2021-45960
gentoo high CVE-2021-45960: 1 GLSA(s) (202209-24), 1 atom(s) (dev-libs/expat); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-45960
redhat medium — https://access.redhat.com/security/cve/CVE-2021-45960
suse medium CVE-2021-45960 severity moderate: SUSE including 320 source package names (0.1.0:libexpat1-2.2.5-3.9.1, 0.1.75:libexpat1-2.2.5-3.9.1, …), 561 product×package rows across 156 product lines (Container bci/bci-init, Container bci/golang, … (156 product lines)): Fixed 391, Known Affected 166, Known Not Affected 4. https://www.suse.com/security/cve/CVE-2021-45960/
ubuntu low CVE-2021-45960 low priority: Ubuntu including 24 source packages (apache2, apr-util, …), 359 status rows across 15 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 117, DNE 92, needs-triage 66, ignored 59, released 25. https://ubuntu.com/security/CVE-2021-45960

Affected software / configurations for CVE-2021-45960

Vendor Product Version Raw CPE
libexpat_project libexpat < 2.4.3 cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*
tenable nessus < 8.15.3 cpe:2.3:a:tenable:nessus:*:*:*:*:*:*:*:*
tenable nessus >= 10.0.0, < 10.1.1 cpe:2.3:a:tenable:nessus:*:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
debian debian_linux 11.0 cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
siemens sinema_remote_connect_server < 3.1 cpe:2.3:a:siemens:sinema_remote_connect_server:*:*:*:*:*:*:*:*
netapp active_iq_unified_manager — cpe:2.3:a:netapp:active_iq_unified_manager:-:*:*:*:*:vmware_vsphere:*:*
netapp hci_baseboard_management_controller h610c cpe:2.3:a:netapp:hci_baseboard_management_controller:h610c:*:*:*:*:*:*:*
netapp hci_baseboard_management_controller h610s cpe:2.3:a:netapp:hci_baseboard_management_controller:h610s:*:*:*:*:*:*:*
netapp hci_baseboard_management_controller h615c cpe:2.3:a:netapp:hci_baseboard_management_controller:h615c:*:*:*:*:*:*:*
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:-:*:*:*:*:*:*:*

References for CVE-2021-45960

URL Tags
http://www.openwall.com/lists/oss-security/2022/01/17/3 Exploit Mailing List Third Party Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1217609 Issue Tracking Permissions Required Third Party Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-484086.pdf Patch Third Party Advisory
https://github.com/libexpat/libexpat/issues/531 Exploit Issue Tracking Patch Third Party Advisory
https://github.com/libexpat/libexpat/pull/534 Patch Third Party Advisory
https://security.gentoo.org/glsa/202209-24 Third Party Advisory
https://security.netapp.com/advisory/ntap-20220121-0004/ Third Party Advisory
https://www.debian.org/security/2022/dsa-5073 Issue Tracking Third Party Advisory
https://www.tenable.com/security/tns-2022-05 Third Party Advisory
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