CVE-2023-4966Known exploitationPublic exploitNetwork attack vector

Session-token disclosure via oversized Host header

Published Oct 10, 2023 · Updated Jul 31, 2026

Buffer over-read in Cloud Software Group NetScaler ADC and NetScaler Gateway allows remote attackers to disclose process memory. The OpenID configuration endpoint uses a truncated output buffer's intended length when forming the response, causing it to include adjacent memory. A customer-managed appliance configured as a Gateway or AAA virtual server is exposed, and leaked NetScaler AAA cookies permit session hijacking without credentials or MFA.

CVSS severity9.4
Critical
EPSS probability100.00%
Next 30 days · Sep 20, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer over-read in Cloud Software Group NetScaler ADC and NetScaler Gateway allows remote attackers to disclose process memory. The OpenID configuration endpoint uses a truncated output buffer's intended length when forming the response, causing it to include adjacent memory. A customer-managed appliance configured as a Gateway or AAA virtual server is exposed, and leaked NetScaler AAA cookies permit session hijacking without credentials or MFA.

The record

CVE
CVE-2023-4966
Published
Oct 10, 2023
Updated
Jul 31, 2026
Vendor
Cloud Software Group
Product
NetScaler Gateway
Classifications
CWE-119, T1539
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 1, 2023Exploitation reportedLockBit 3.0 affiliate exploitation
  2. Oct 10, 2023CVE publishedPublication date reported by the CVE source.
  3. Jul 31, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=13.0 <92.19
  2. Affected versionversion=13.1 <49.15
  3. Affected versionversion=14.1 <8.50

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Cloud Software Group · NetScaler Gatewayversion=13.0 <92.19; version=13.1 <49.15; version=14.1 <8.50
Cloud Software Group · NetScaler ADCversion=12.1-FIPS <55.300; version=12.1-NDcPP <55.300; version=13.0 <92.19; version=13.1 <49.15; version=13.1-FIPS <37.164; version=14.1 <8.50

Published CVSS scores

9.4CitrixCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsShadowserver observations through Sep 20, 2026. Gaps indicate unavailable data.
Sep 14, 2026Sep 20, 2026
View daily counts
Reporting dayUnique IPs
Sep 14, 202630
Sep 15, 20264
Sep 16, 20266
Sep 17, 202625
Sep 18, 202628
Sep 19, 202628
Sep 20, 202629
Latest reporting daySep 20, 2026
Latest daily unique IPs29
Prior 30-day average12.5
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1539Steal Web Session Cookie

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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