CVE WatchSep 27, 2026

CVE-2026-88771

Citrix NetScaler Improper Input Validation Vulnerability

CVSS

—

No CVSS

EPSS

—

KEV

YES

Sep 27, 2026

Exploit Today

0-100

Published: Sep 27, 2026 · Last modified: Sep 27, 2026 · CWE-20

EPSS · 30d

Not enough EPSS history yet.

KEV catalog record

Product

Citrix / NetScaler

Vulnerability

Citrix NetScaler Improper Input Validation Vulnerability

Added to KEV

Sep 27, 2026

Remediate by

Sep 30, 2026

Known ransomware use

Summary description

Citrix NetScaler ADC and NetScaler Gateway contain an improper input validation vulnerability that could allow an unauthenticated attacker to execute arbitrary commands.

Required action

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Notes

Running the provided IOCs in the NetScaler console may help identify indicators of exploitation. Customers must conduct forensic triage as directed by BOD 26‑04 and follow Citrix’s published guidance for mitigations. For more information, please see: https://community.citrix.com/techzone-blogs/110_security-updates/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve-2026-88771-through-cve-2026-88778 ; https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX697096 ; https://support.citrix.com/external/article/CTX694799/steps-to-take-if-netscaler-adc-is-suspec.html ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-88772

Technical description

Improper input validation vulnerability in Citrix NetScaler ADC and Citrix NetScaler Gateway. This issue affects ADC: before 14.1-73.37, before 13.1-64.23, before 14.1-73.37 FIPS, and before 13.1.37.279 FIPS and NDcPP; Gateway: before 14.1-73.37 and before 13.1-64.23 leading to an unauthenticated attacker to execute arbitrary commands.

Official references

Related CVEs

CVECVSSEPSSKEVRExploitTitleMod.

CVE-2026-88772—

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KEV—50Citrix NetScaler Improper Restriction of Operations within the Bounds of a Memory Buffer Vulnerability5h CVE-2026-101041—

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——0The account recovery (password reset) functionality in the vulnerability-lookup web application contains a time-of-check-to-time-of-use (TOCTOU) race condition in the consumption of single-use recovery tokens. The original implementation verified the token nonce against the stored digest and then consumed (cleared) it in separate database operations. Two concurrent HTTP requests presenting the same valid recovery token could both pass the verification check before either transaction committed, allowing both to set their own password on the target account. The last transaction to commit overwrites the first, enabling an attacker who possesses a valid recovery token to replace the legitimate user's password with one of their choosing. A secondary defect in the same endpoint (confirm_account) allowed a valid recovery link to be used to set an empty or trivially short password (e.g., three characters). The view handler performed only a manual equality comparison between the two password fields and never invoked the form's validation logic, bypassing the intended minimum-length and complexity constraints. The affected component is the user account recovery endpoint (/user/confirm_account/<token>) and the associated token verification and consumption logic in the User model (website/models/user.py) and the view layer (website/web/views/user.py).13h CVE-2026-1008338.2 HIG

12.0%

——4Contrast (edgelesssys/contrast) versions 1.14.0 before 1.23.1 generate runtime policies that fail to detect all container image substitutions. A bad rebase during a Kata Containers update accidentally introduced an `allow_storage` rule that accepts storage entries using the `image_guest_pull` driver without verifying the image digest. An attacker with access to the Kata agent API — for example, a Kubernetes cluster administrator in Contrast's threat model — can therefore substitute a container image with an exploit payload, provided the substituted image satisfies the remaining policy rules, undermining the confidential container's integrity guarantees.1d CVE-2026-1006995.3 MED

8.0%

——2Nodemailer is a Node.js email-sending library. In versions >= 9.1.0 and < 10.0.9, the address parser (src/addressparser) mishandles addresses whose local-part is a quoted string and that are followed by RFC 5322 comments, allowing trailing comment-separated domain atoms to be retained in the normalized address. For example, the input "user"@example.com(x)evil.com is parsed to the address value 'user@example.com evil.com', which contains additional attacker-controlled domain text separated by a literal space. This parsed value is used without further strict recipient validation when the message envelope is built (envelope.to in src/mime-node), so a malformed/ambiguous recipient address can be accepted and placed in the SMTP envelope. Whether this results in delivery to an unintended recipient on real SMTP servers has not been confirmed. The issue is a variant of the RFC 5322 comment parsing problem addressed in GHSA-cc9r-2j5m-2m83, affecting the separate quoted-local-part code path. Version 10.0.9 contains a fix.2d CVE-2026-1006647.5 HIG

23.5%

——7Netty's HTTP/3 codec (io.netty:netty-codec-http3) versions 4.2.2.Final through 4.2.17.Final builds the HTTP/3 :authority pseudo-header from the HTTP/1 Host header before considering the authority of an absolute-form HTTP/1 request-target. In HttpConversionUtil.toHttp3Headers(HttpMessage, boolean) — reached via Http3FrameToHttpObjectCodec(false) — a non-empty Host header takes precedence over the request-target authority, contrary to the HTTP/1.1 rule that a server receiving an absolute-form request-target must ignore the Host header. In a Netty-based HTTP/1-to-HTTP/3 gateway, proxy, or protocol bridge, a remote client can send a request such as "GET https://trusted.example/admin HTTP/1.1" with "Host: attacker.example", causing components that validate, authorize, or route on the RFC-defined request-target authority to reach a different decision than the upstream HTTP/3 peer, which receives :authority derived from the conflicting Host header. This authority confusion can affect virtual-host routing, allow-list checks, backend selection, cache keys, and URL generation. The advisory reports integrity impact only (no code execution, memory corruption, or availability impact). Fixed in 4.2.18.Final.11h CVE-2026-1006637.5 HIG

20.5%

——6Netty's HTTP/3 codec (io.netty:netty-codec-http3) from 4.2.2.Final through 4.2.17.Final does not special-case HTTP/1 CONNECT authority-form request-targets when converting HTTP/1 messages to HTTP/3 in HttpConversionUtil.toHttp3Headers. The authority-form target (e.g., "CONNECT trusted.example:443") is parsed as a URI, so its host is emitted as :scheme, :path is set to "/", and the HTTP/1 Host header is used as :authority; if no Host header is present the CONNECT target is dropped. In a Netty-based HTTP/1-to-HTTP/3 proxy or gateway, a remote client can send a CONNECT request whose Host header names a different authority than the request-target, producing a malformed HTTP/3 CONNECT whose tunnel :authority is attacker-controlled. This can bypass tunnel allow-lists, egress policy, backend selection, or audit controls that validate the HTTP/1 CONNECT request-target before forwarding over HTTP/3. The issue is fixed in 4.2.18.Final.11h