Vulnerability · Published Jan 1, 2022 · Assigned by mitre

CVE-2021-45960

High 8.8

In plain English

A high-severity security flaw in the expat package (AlmaLinux). Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 4.7% (higher than 92% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.8High

Exploit odds (30 days)4.7%top 8.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack tooling1Public PoC

Official 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 memory).

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
AlmaLinux:8	expat	2.2.5-8.el8_6.2	ALSA-2022:0951
AlmaLinux:8	expat-devel	2.2.5-8.el8_6.2	ALSA-2022:0951
Alpine:v3.20	expat	2.4.3-r0	ALPINE-CVE-2021-45960
Alpine:v3.21	expat	2.4.3-r0	ALPINE-CVE-2021-45960
Alpine:v3.22	expat	2.4.3-r0	ALPINE-CVE-2021-45960
Alpine:v3.23	expat	2.4.3-r0	ALPINE-CVE-2021-45960
Alpine:v3.24	expat	2.4.3-r0	ALPINE-CVE-2021-45960
Debian:12	expat	2.4.3-1	DEBIAN-CVE-2021-45960
Debian:13	expat	2.4.3-1	DEBIAN-CVE-2021-45960
Debian:14	expat	2.4.3-1	DEBIAN-CVE-2021-45960
Debian:12	libxmltok	no fix listed	DEBIAN-CVE-2021-45960
Rocky Linux:8	expat	0:2.2.5-4.el8_5.3	RLSA-2022:0951
Ubuntu:22.04:LTS	cadaver	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:24.04:LTS	cadaver	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:25.10	cadaver	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:26.04:LTS	cadaver	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:26.10	cadaver	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:22.04:LTS	expat	2.4.3-1	UBUNTU-CVE-2021-45960
Ubuntu:22.04:LTS	firefox	1:1snap1-0ubuntu1	UBUNTU-CVE-2021-45960
Ubuntu:22.04:LTS	matanza	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:24.04:LTS	matanza	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:25.10	matanza	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:26.04:LTS	matanza	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:26.10	matanza	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:25.10	swish-e	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:26.10	swish-e	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:22.04:LTS	tdom	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:24.04:LTS	tdom	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:25.10	tdom	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:26.04:LTS	tdom	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:26.10	tdom	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:22.04:LTS	wbxml2	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:24.04:LTS	wbxml2	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:25.10	wbxml2	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:26.04:LTS	wbxml2	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:26.10	wbxml2	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:25.10	xmlrpc-c	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:26.04:LTS	xmlrpc-c	no fix listed	UBUNTU-CVE-2021-45960
Ubuntu:26.10	xmlrpc-c	no fix listed	UBUNTU-CVE-2021-45960

Affected products (as reported)

Vendor	Product	Versions
n/a	n/a	n/a

Weakness: CWE-682 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

References

https://github.com/libexpat/libexpat/issues/531 x_refsource_MISC
https://github.com/libexpat/libexpat/pull/534 x_refsource_MISC
https://bugzilla.mozilla.org/show_bug.cgi?id=1217609 x_refsource_MISC
[oss-security] 20220117 Expat 2.4.3 released, includes 8 security fixes mailing-list, x_refsource_MLIST
https://security.netapp.com/advisory/ntap-20220121-0004/ x_refsource_CONFIRM
https://www.tenable.com/security/tns-2022-05 x_refsource_CONFIRM
DSA-5073 vendor-advisory, x_refsource_DEBIAN
https://cert-portal.siemens.com/productcert/pdf/ssa-484086.pdf x_refsource_CONFIRM
GLSA-202209-24 vendor-advisory, x_refsource_GENTOO
https://cert-portal.siemens.com/productcert/html/ssa-484086.html
https://cert-portal.siemens.com/productcert/html/ssa-398330.html