CVE-2023-28321: An improper certificate validation vulnerability exists in curl <v8.1.0 in the way it supports matching of wil

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MEDIUM 5.9REMOTEWATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2023-28321 is a medium-severity flaw (CVSS 5.9) affecting curl, debian linux, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An improper certificate validation vulnerability exists in curl <v8.1.0 in the way it supports matching of wildcard patterns when listed as "Subject Alternative Name" in TLS server certificates. curl can be built to use its own name matching function for TLS rather than one provided by a TLS library. This private wildcard matching function would match IDN (International Domain Name) hosts incorrectly and could as a result accept patterns that oth

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	1.8% (top 22%)
CISA exploited list	No
Weakness	CWE-295
Published	2023-05-26
Last modified	2026-10-23

Publisher (CNA): HackerOne · Vendor: debian · fedoraproject · haxx · netapp

Am I affected?

Timeline

2023-05-26 21:15 UTCPublished CVE record published
2026-10-23 23:10 UTCUpdated Record last modified

haxx curl UPGRADE

Affected: < 8.1.0

Fixed in: 8.1.0

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 8.1.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade curl

Note

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

debian debian linux MITIGATE

Affected: 10.0

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.

fedoraproject fedora MITIGATE

Affected: 37 · 38

Fixed in: no fixed release known

Safe to downgrade to: a release before 37

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.

netapp clustered data ontap MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy clustered-data-ontap || rpm -q clustered-data-ontap || clustered-data-ontap --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

netapp ontap antivirus connector MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy ontap-antivirus-connector || rpm -q ontap-antivirus-connector || ontap-antivirus-connector --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

netapp h300s firmware MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

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.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · python-openslide · FIXED · 1.4.7-1.fc46 · FEDORA-2026-336bea884e · source

sudo dnf upgrade --advisory=FEDORA-2026-336bea884e

Fedora ELN · valgrind · FIXED · 3.28.0-1.eln159 · FEDORA-2026-c593ef1d15 · source

sudo dnf upgrade --advisory=FEDORA-2026-c593ef1d15

Ubuntu 20.04 · curl · FIXED · 7.68.0-1ubuntu2.19

sudo apt update && sudo apt install --only-upgrade curl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' curl)" ge "7.68.0-1ubuntu2.19" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 22.04 · curl · FIXED · 7.81.0-1ubuntu1.11

sudo apt update && sudo apt install --only-upgrade curl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' curl)" ge "7.81.0-1ubuntu1.11" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 24.04 · curl · FIXED · 7.88.1-10ubuntu1

sudo apt update && sudo apt install --only-upgrade curl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' curl)" ge "7.88.1-10ubuntu1" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 24.10 · curl · FIXED · 7.88.1-10ubuntu1

sudo apt update && sudo apt install --only-upgrade curl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' curl)" ge "7.88.1-10ubuntu1" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 25.04 · curl · FIXED · 7.88.1-10ubuntu1

sudo apt update && sudo apt install --only-upgrade curl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' curl)" ge "7.88.1-10ubuntu1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · curl · FIXED · 7.88.1-10

sudo apt update && sudo apt install --only-upgrade curl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' curl)" ge "7.88.1-10" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · curl · FIXED · 7.88.1-10

sudo apt update && sudo apt install --only-upgrade curl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' curl)" ge "7.88.1-10" && echo PATCHED || echo STILL-VULNERABLE

RHEL 8 · curl · FIXED · curl-7.61.1-30.el8_8.3

sudo dnf upgrade --advisory=RHSA-2023:4523 rpm -q curl

RHEL 8.6 Extended Update Support · curl · FIXED · curl-7.61.1-22.el8_6.9

sudo dnf upgrade --advisory=RHSA-2023:6292 rpm -q curl

RHEL 9 · curl · FIXED · curl-7.76.1-23.el9_2.2

sudo dnf upgrade --advisory=RHSA-2023:4354 rpm -q curl

RHEL 9.0 Extended Update Support · curl · FIXED · curl-7.76.1-14.el9_0.7

sudo dnf upgrade --advisory=RHSA-2023:5598 rpm -q curl

RHEL 6 · curl · DEFERRED

Alpine 3.20 · curl · FIXED · curl-8.1.0-r0

apk add --upgrade curl apk info -v curl

Alpine 3.21 · curl · FIXED · curl-8.1.0-r0

apk add --upgrade curl apk info -v curl

Alpine 3.22 · curl · FIXED · curl-8.1.0-r0

apk add --upgrade curl apk info -v curl

Alpine 3.23 · curl · FIXED · curl-8.1.0-r0

apk add --upgrade curl apk info -v curl

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2023-270 · source

sudo dnf update --advisory=ALAS2023-2023-270

Amazon Linux 2 · see advisory · FIXED · ALAS2-2023-2230 · source

sudo yum update --advisory=ALAS2-2023-2230

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.

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References

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