CVE-2022-25236: xmlparse.c in Expat (aka libexpat) before 2.4.5 allows attackers to insert namespace-separator characters into

Q: How do I fix CVE-2022-25236?

libexpat: upgrade to 2.4.5; debian linux: mitigate or apply the listed mitigation; http server: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2022-25236 being exploited?

CVE-2022-25236 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2022-25236 affect?

CVE-2022-25236 affects libexpat, debian linux, http server. Severity is critical (CVSS 9.8). xmlparse.c in Expat (aka libexpat) before 2.4.5 allows attackers to insert namespace-separator characters into namespace URIs.

Q: How urgent is CVE-2022-25236?

Priority 72/100. Critical severity; EPSS top 2%: very likely to be exploited; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist

This week

CRITICAL 9.8REMOTEWATCHLISTUPGRADEMITIGATEDOWNGRADE

CVE-2022-25236 is a critical-severity flaw (CVSS 9.8) affecting libexpat, debian linux, http server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

xmlparse.c in Expat (aka libexpat) before 2.4.5 allows attackers to insert namespace-separator characters into namespace URIs.

Why this priority

Critical severity
EPSS top 2%: very likely to be exploited
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	35.3% (top 2%)
CISA exploited list	No
Weakness	CWE-668
Published	2022-02-16
Last modified	2026-10-14

Publisher (CNA): MITRE · Vendor: debian · libexpat project · oracle · siemens

Last updated 2026-10-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-02-16 01:15 UTCPublished CVE record published
2026-10-14 17:17 UTCUpdated Record last modified

libexpat project libexpat UPGRADE

Affected: < 2.4.5

Fixed in: 2.4.5

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy libexpat || rpm -q libexpat || libexpat --version

2. UPGRADE to 2.4.5 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade libexpat

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libexpat

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

debian debian linux MITIGATE

Affected: 10.0 · 11.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

oracle http server DOWNGRADE

Affected: 12.2.1.3.0 · 12.2.1.4.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 12.2.1.3.0

1. Check installed version

apt-cache policy http-server || rpm -q http-server || http-server --version

2. No fixed release: DOWNGRADE to a release before 12.2.1.3.0 (Debian / Ubuntu)

apt-cache madison http-server sudo apt install http-server=<VERSION_BEFORE_12.2.1.3.0> sudo apt-mark hold http-server

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list http-server sudo dnf downgrade http-server-<VERSION_BEFORE_12.2.1.3.0> sudo dnf versionlock add http-server

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

oracle zfs storage appliance kit DOWNGRADE

Affected: 8.8

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.8

1. Check installed version

apt-cache policy zfs-storage-appliance-kit || rpm -q zfs-storage-appliance-kit || zfs-storage-appliance-kit --version

2. No fixed release: DOWNGRADE to a release before 8.8 (Debian / Ubuntu)

apt-cache madison zfs-storage-appliance-kit sudo apt install zfs-storage-appliance-kit=<VERSION_BEFORE_8.8> sudo apt-mark hold zfs-storage-appliance-kit

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list zfs-storage-appliance-kit sudo dnf downgrade zfs-storage-appliance-kit-<VERSION_BEFORE_8.8> sudo dnf versionlock add zfs-storage-appliance-kit

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

siemens sinema remote connect server UPGRADE

Affected: < 3.1

Fixed in: 3.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy sinema-remote-connect-server || rpm -q sinema-remote-connect-server || sinema-remote-connect-server --version

2. UPGRADE to 3.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade sinema-remote-connect-server

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade sinema-remote-connect-server

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · nemo · FIXED · 6.8.0-1.fc46 · FEDORA-2026-0edead723f · source

sudo dnf upgrade --advisory=FEDORA-2026-0edead723f

Fedora ELN · composer · FIXED · 2.11.1-1.eln159 · FEDORA-2026-cb4f992456 · source

sudo dnf upgrade --advisory=FEDORA-2026-cb4f992456

Ubuntu 20.04 · expat · FIXED · 2.2.9-1ubuntu0.2

sudo apt update && sudo apt install --only-upgrade expat dpkg --compare-versions "$(dpkg-query -W -f='${Version}' expat)" ge "2.2.9-1ubuntu0.2" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 22.04 · expat · FIXED · 2.4.5-2

sudo apt update && sudo apt install --only-upgrade expat dpkg --compare-versions "$(dpkg-query -W -f='${Version}' expat)" ge "2.4.5-2" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 24.04 · expat · FIXED · 2.4.5-2

sudo apt update && sudo apt install --only-upgrade expat dpkg --compare-versions "$(dpkg-query -W -f='${Version}' expat)" ge "2.4.5-2" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 24.10 · expat · FIXED · 2.4.5-2

sudo apt update && sudo apt install --only-upgrade expat dpkg --compare-versions "$(dpkg-query -W -f='${Version}' expat)" ge "2.4.5-2" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 25.04 · expat · FIXED · 2.4.5-2

sudo apt update && sudo apt install --only-upgrade expat dpkg --compare-versions "$(dpkg-query -W -f='${Version}' expat)" ge "2.4.5-2" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · expat · FIXED · 2.4.5-1

sudo apt update && sudo apt install --only-upgrade expat dpkg --compare-versions "$(dpkg-query -W -f='${Version}' expat)" ge "2.4.5-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · expat · FIXED · 2.4.5-1

sudo apt update && sudo apt install --only-upgrade expat dpkg --compare-versions "$(dpkg-query -W -f='${Version}' expat)" ge "2.4.5-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · libxmltok · NO FIX YET

RHEL 6 Extended Lifecycle Support · expat · FIXED · expat-2.0.1-14.el6_10

sudo dnf upgrade --advisory=RHSA-2022:1309 rpm -q expat

RHEL 7 · firefox · FIXED · firefox-91.7.0-3.el7_9

sudo dnf upgrade --advisory=RHSA-2022:0824 rpm -q firefox

RHEL 7 · thunderbird · FIXED · thunderbird-91.7.0-2.el7_9

sudo dnf upgrade --advisory=RHSA-2022:0850 rpm -q thunderbird

RHEL 7 · expat · FIXED · expat-2.1.0-14.el7_9

sudo dnf upgrade --advisory=RHSA-2022:1069 rpm -q expat

RHEL 8 · firefox · FIXED · firefox-91.7.0-3.el8_5

sudo dnf upgrade --advisory=RHSA-2022:0818 rpm -q firefox

Alpine 3.20 · expat · FIXED · expat-2.4.5-r0

apk add --upgrade expat apk info -v expat

Alpine 3.21 · expat · FIXED · expat-2.4.5-r0

apk add --upgrade expat apk info -v expat

Alpine 3.22 · expat · FIXED · expat-2.4.5-r0

apk add --upgrade expat apk info -v expat

Alpine 3.23 · expat · FIXED · expat-2.4.5-r0

apk add --upgrade expat apk info -v expat

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2023-058 · source

sudo dnf update --advisory=ALAS2023-2023-058

Amazon Linux 2 · see advisory · FIXED · ALAS2-2022-1779 · source

sudo yum update --advisory=ALAS2-2022-1779

Amazon Linux 1 · see advisory · FIXED · ALAS-2022-1573 · source

sudo yum update --advisory=ALAS-2022-1573

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: Satheesh575555/external_expat_AOSP10_r33_CVE-2022-25236 (0 stars)
Write-up: www.oracle.com/security-alerts/cpuapr2022.html

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2022-25236?

libexpat: upgrade to 2.4.5; debian linux: mitigate or apply the listed mitigation; http server: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2022-25236 being exploited?

CVE-2022-25236 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2022-25236 affect?

CVE-2022-25236 affects libexpat, debian linux, http server. Severity is critical (CVSS 9.8). xmlparse.c in Expat (aka libexpat) before 2.4.5 allows attackers to insert namespace-separator characters into namespace URIs.

How urgent is CVE-2022-25236?

Priority 72/100. Critical severity; EPSS top 2%: very likely to be exploited; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Debian vulnerabilities · Siemens vulnerabilities

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References

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