Improper Restriction of Operations within the Bounds of a Memory Buffer in NetScaler ADC and NetScaler Gateway allows Unauthenticated Denial of Service and Out-Of-Bounds Memory Read
CVE-2023-6549
“▲” beside the score: it is higher than NVD's CVSS score.
Score elevated to 9.0 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2024-01-17), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 8.2 retained for reference. The 9.0 is the floor for confirmed exploitation, not an impact rating: this CVE's impact severity (EG Severity) is CVSS 8.2 HIGH under GitHub Security Advisory CVSS. Confidence: HIGH.
- 2,818 internet-facing services (distinct ip:port) on record running an affected version — derived from Shodan data (© Shodan); a patched service can stay counted while its port stays open
- Actively exploited in the wild (CISA-KEV) — the reason this is sooner than the SSVC decision on this page at low or medium mission impact
No fix is confirmed yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for the fix.
The CVE record's CNA (Citrix Systems, Inc.) lists Cloud Software Group NetScaler ADC versions 14.1 up to but not including 12.35, 13.1 up to but not including 51.15, 13.0 up to but not including 92.21, 13.1-FIPS up to but not including 37.176 and 2 more ranges as affected. No release containing a fix is confirmed on record.
2,818 internet-facing services (distinct ip:port) on record running a version that maps to CVE-2023-6549, in our KEV-Exposure radar’s Shodan-derived sample.
How it counts: every 12 hours, when Shodan query credits allow, the radar runs one Shodan query per tracked product, reads up to 100 ip:port services per query, and keeps a service when its banner version matches a CISA-KEV or high-EPSS CVE; a service is dropped when neither a search nor a Shodan InternetDB port re-check has refreshed it for 21 days. A re-check that finds the port still listed by Shodan InternetDB refreshes the service without re-reading the banner, so a patched service can stay counted while its port stays open. A count is a banner-version inference over a sample, not an exploit test and not an internet-wide census, and the unit is a service, not a machine: a machine answering on two ports counts twice.
- CVSS v3
- 8.2
- EG Score
- 9.0CRITICALhigh confidence
- EG Risk
- 92EG Risk 92/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity82% × 45%Impact severity (EG Severity): CVSS 8.2 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation100% × 40%Fixed at 100% for a CISA KEV listing: EchelonGraph's rule.Automatability100% × 15%CISA's SSVC Automatable value: yes (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Attend at low or medium mission impact; Act at high (mission-essential systems).Exploitation active (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation sooner than your standard update timelines at low or medium mission impact and as soon as possible at high, and watch the vendor's advisory for the fix. - EPSS PROB
- 58%
- EPSS %ILE
- 99th
- KEV
- ⚠ Exploited
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (9.0): severity, escalated by confirmed exploitation. This CVE's 9.0 is the CISA KEV floor for confirmed exploitation, not an impact rating: its impact severity (EG Severity) is CVSS 8.2 HIGH.
- EG Severity
- 8.2 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 58% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-20). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- CISA KEV and EG-KEV Tier 1 (exploited in the wild)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Attend at medium mission impactAttend at low or medium mission impact; Act at high (mission-essential systems).CISA BOD 26-04: 3 days if the affected system is publicly exposed; 14 days if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Attend at low or medium mission impact; Act at high (mission-essential systems).
No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation sooner than your standard update timelines at low or medium mission impact and as soon as possible at high, and watch the vendor's advisory for the fix.
Exploitation active (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)3 days if the affected system is publicly exposed; 14 days if it is not.
In CISA KEV yes (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
CISA required action“Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.”
Quoted verbatim from CISA's Known Exploited Vulnerabilities catalog. CISA directs it at US federal civilian executive branch agencies under Binding Operational Directive (BOD) 26-04, which replaced BOD 22-01 on 10 June 2026; it is not EchelonGraph's advice. CISA's notes: https://support.citrix.com/article/CTX584986/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20236548-and-cve20236549 · https://nvd.nist.gov/vuln/detail/CVE-2023-6549
Published
January 17, 2024
Last Modified
February 26, 2026
Advisory Details (2)
Auto-updated Oct 19, 2026Known Exploited Vulnerabilities Catalog | CISA
Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-6549Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 19× in last 7d / 188× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 100 of 1,060 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 960 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-10-21 00:26 UTCEG score recompute
- 2026-10-21 00:26 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-20 16:30 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-19 22:26 UTCEG score recompute
- 2026-10-19 22:26 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-19 16:29 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-18 20:29 UTCEG score recompute
- 2026-10-18 20:29 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-18 07:38 UTCEG score recompute
- 2026-10-17 18:31 UTCEG score recompute
- 2026-10-17 18:31 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-17 16:30 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-16 16:36 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-16 16:35 UTCEG score recompute
- 2026-10-16 16:35 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-15 16:29 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-15 14:37 UTCEG score recompute
- 2026-10-15 14:36 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-14 16:30 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-14 12:38 UTCEG score recompute
- 2026-10-14 12:38 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-13 16:30 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-13 10:41 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-12 18:10 UTCEG score recompute
- 2026-10-12 08:42 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
Show 75 moreShow fewer
- 2026-10-12 04:39 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-12 00:38 UTCEG score recompute
- 2026-10-12 00:37 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-11 20:35 UTCEG score recompute
- 2026-10-11 20:35 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-11 16:34 UTCEG score recompute
- 2026-10-11 16:33 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-11 13:45 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-11 12:30 UTCEG score recompute
- 2026-10-11 12:30 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-11 08:28 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-11 04:27 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-11 00:22 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-10 20:20 UTCEG score recompute
- 2026-10-10 20:20 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-10 19:58 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-10 16:18 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-10 12:17 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-10 08:15 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-10 04:13 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-10 00:12 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-09 20:11 UTCEG score recompute
- 2026-10-09 20:10 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-09 20:05 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-09 16:09 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-09 12:07 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-09 08:06 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-09 04:05 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-09 00:02 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-08 20:01 UTCEG score recompute
- 2026-10-08 20:01 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-08 17:06 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-08 15:56 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-08 11:54 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-08 07:53 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-08 03:52 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-07 23:51 UTCEG score recompute
- 2026-10-07 23:51 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-07 23:46 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-07 19:50 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-07 15:48 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-07 11:42 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-07 07:41 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-07 03:40 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-06 23:38 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-06 19:37 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-06 15:36 UTCEG score recompute
- 2026-10-06 15:36 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-06 15:15 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-06 11:35 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-06 07:33 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-06 03:32 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-05 23:29 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-05 19:28 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-05 15:27 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-05 11:23 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-05 07:22 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-05 03:20 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-04 23:19 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-04 19:17 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-04 15:14 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-04 11:12 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-04 07:11 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-04 03:10 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-03 23:08 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-03 19:04 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-03 15:02 UTCEG score recompute
- 2026-10-03 15:02 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-03 14:23 UTCEPSS rescoreEPSS 58% · 99th percentile
- 2026-10-03 10:59 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-03 06:58 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-03 02:56 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-02 22:54 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-02 18:53 UTCEG score recompute
- 2026-10-02 18:53 UTCGHSA enrichmentGHSA-8fxh-p33g-qf5m · GitHub severity HIGH · GitHub CVSS 8.2
Public detection templates
(1 reference)A public Nuclei detection template is referenced for this CVE. A detection template checks whether a system is affected; it is not necessarily exploit code.
- Nucleihttp/cves/2023/CVE-2023-6549.yamlPublished Oct 15, 2025
Citrix Netscaler ADC & Gateway - Out-Of-Bounds Memory Read
Open source ↗
Related CVEs(same CWE)
Frequently asked(6)
What is CVE-2023-6549?
When was the CVE record for CVE-2023-6549 published?
Is CVE-2023-6549 actively exploited?
What is the CVSS score of CVE-2023-6549?
Which products are affected by CVE-2023-6549?
How do I remediate CVE-2023-6549?
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2023-6549
Is Your Infrastructure Affected by CVE-2023-6549?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.