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CVE-2023-28320: A denial of service vulnerability exists in curl <v8.1.0 in the way libcurl provides several different backend

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MEDIUM 5.9REMOTEUPGRADEUPGRADEMITIGATE

CVE-2023-28320 is a medium-severity flaw (CVSS 5.9) affecting curl, macos, clustered data ontap. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A denial of service vulnerability exists in curl <v8.1.0 in the way libcurl provides several different backends for resolving host names, selected at build time. If it is built to use the synchronous resolver, it allows name resolves to time-out slow operations using `alarm()` and `siglongjmp()`. When doing this, libcurl used a global buffer that was not mutex protected and a multi-threaded application might therefore crash or otherwise misbehave

Why this priority

  • Public exploit reference
  • Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score5.9 (Medium)
Attack vectorNetwork (remote)
Attack complexityHigh
Privileges neededNone
User interactionNone
EPSS exploit chance2.7% (top 14%)
CISA exploited listNo
WeaknessCWE-400, CWE-362
Published2023-05-26
Last modified2026-10-23
Publisher (CNA): HackerOne · Vendor: apple · haxx · netapp

Last updated 2026-10-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

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.
apple macos UPGRADE
Affected: >= 11.0 and < 11.7.9 · >= 12.0 and < 12.6.8 · >= 13.0 and < 13.5
Fixed in: 11.7.9, 12.6.8, 13.5
Safe to downgrade to: a release before 11.0
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.
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.
netapp h500s 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 · NOT AFFECTED
Ubuntu 22.04 · curl · NOT AFFECTED
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 6 · curl · DEFERRED
RHEL 7 · curl · NOT AFFECTED
RHEL 8 · curl · NOT AFFECTED
RHEL 9 · curl · NOT AFFECTED
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
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-2023-28320?

curl: upgrade to 8.1.0; macos: upgrade to 11.7.9, 12.6.8, 13.5; clustered data ontap: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-28320 being exploited?

CVE-2023-28320 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-2023-28320 affect?

CVE-2023-28320 affects curl, macos, clustered data ontap. Severity is medium (CVSS 5.9). A denial of service vulnerability exists in curl <v8.1.0 in the way libcurl provides several different backends for resolving host names, selected at build time. If it is built to use the synchronous resolver, it allows name resolves to tim

How urgent is CVE-2023-28320?

Priority 52/100. Public exploit reference; Remotely exploitable, no login, no user action

Software pages

macOS vulnerabilities · curl vulnerabilities

Related CVEs

References

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