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CVE-2026-3055: Citrix NetScaler Out-of-Bounds Read Vulnerability

97
Patch now
CRITICAL 9.8EXPLOITEDREMOTEUPGRADEUPGRADE

CVE-2026-3055 is a critical-severity flaw (CVSS 9.8) affecting netscaler application delivery controller, netscaler gateway, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Insufficient input validation in NetScaler ADC and NetScaler Gateway when configured as a SAML IDP leading to memory overread

Why this priority

  • Critical severity
  • EPSS top 1%: very likely to be exploited
  • Exploited in the wild (CISA KEV)
  • Public exploit reference
  • CISA SSVC: automatable with total technical impact
  • Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score9.8 (Critical)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance91.5% (top 1%)
CISA exploited listYes, fix due 2026-04-02
WeaknessCWE-125
Published2026-03-23
Last modified2026-06-17
Publisher (CNA): NetScaler · Vendor: citrix

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Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

citrix netscaler application delivery controller UPGRADE
Affected: >= 13.1 and < 13.1-37.262 · >= 13.1 and < 13.1-62.23 · >= 14.1 and < 14.1-60.58
Fixed in: 13.1-37.262, 13.1-62.23, 14.1-60.58
Safe to downgrade to: a release before 13.1
1. Check installed version
apt-cache policy netscaler-application-delivery-controller || rpm -q netscaler-application-delivery-controller || netscaler-application-delivery-controller --version
2. UPGRADE to 13.1-37.262 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade netscaler-application-delivery-controller
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade netscaler-application-delivery-controller
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 13.1 (Debian / Ubuntu)
apt-cache madison netscaler-application-delivery-controller sudo apt install netscaler-application-delivery-controller=<VERSION_BEFORE_13.1> sudo apt-mark hold netscaler-application-delivery-controller
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list netscaler-application-delivery-controller sudo dnf downgrade netscaler-application-delivery-controller-<VERSION_BEFORE_13.1> sudo dnf versionlock add netscaler-application-delivery-controller
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.
citrix netscaler gateway UPGRADE
Affected: >= 13.1 and < 13.1-62.23 · >= 14.1 and < 14.1-60.58
Fixed in: 13.1-62.23, 14.1-60.58
Safe to downgrade to: a release before 13.1
1. Check installed version
apt-cache policy netscaler-gateway || rpm -q netscaler-gateway || netscaler-gateway --version
2. UPGRADE to 13.1-62.23 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade netscaler-gateway
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade netscaler-gateway
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 13.1 (Debian / Ubuntu)
apt-cache madison netscaler-gateway sudo apt install netscaler-gateway=<VERSION_BEFORE_13.1> sudo apt-mark hold netscaler-gateway
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list netscaler-gateway sudo dnf downgrade netscaler-gateway-<VERSION_BEFORE_13.1> sudo dnf versionlock add netscaler-gateway
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.

Exact fixes by distribution

Fedora ELN · perl-Encode · FIXED · 3.25-528.eln159 · FEDORA-2026-79991d0238 · source
sudo dnf upgrade --advisory=FEDORA-2026-79991d0238
Fedora 46 · fonttools · FIXED · 4.68.0-1.fc46 · FEDORA-2026-65d6c01c75 · source
sudo dnf upgrade --advisory=FEDORA-2026-65d6c01c75

Public exploits and detection

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

Advisories and coverage

Research and news

Verify at the official source NVD · CVE Program · CISA KEV catalog · 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-2026-3055?

netscaler application delivery controller: upgrade to 13.1-37.262, 13.1-62.23, 14.1-60.58; netscaler gateway: upgrade to 13.1-62.23, 14.1-60.58. Exact commands for each OS are on this page.

Is CVE-2026-3055 being exploited?

Yes. CVE-2026-3055 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2026-3055 affect?

CVE-2026-3055 affects netscaler application delivery controller, netscaler gateway. Severity is critical (CVSS 9.8). Insufficient input validation in NetScaler ADC and NetScaler Gateway when configured as a SAML IDP leading to memory overread

How urgent is CVE-2026-3055?

Priority 97/100. Critical severity; EPSS top 1%: very likely to be exploited; Exploited in the wild (CISA KEV); Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Software pages

Citrix vulnerabilities

Related CVEs

References

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