CVE-2026-76490VulnerabilityPublished 21 Oct 2026Updated 7 Nov 2026

As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco Expressway Series software

Source GCVE Database

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Authoritative record:CVE-2026-76490· High 8.6

Not known to be exploited · CVSS 8.6 High.

Data as of 7 Nov 2026, 19:47 UTC

CVSS 3.1 base score

8.6High

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (cisco)	CVSS 3.1	8.6

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 21 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 7 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-4h68-8g8q-39mj

What to do

Affected software

Product	Affected	Fixed in
CiscoCisco TelePresence Video Communication Server (VCS) Expressway	Affected X8.1 – X15.5.2 93 affected builds	Fixed in–

AI-suggested

Cisco has released software hardening updates addressing these vulnerabilities as part of their internal security review. Although specific patch versions are not listed, users should apply the latest Cisco Expressway Series software updates to remediate this issue. Patch status is not explicitly confirmed in the data; therefore, users should consult Cisco's official advisories for current remediation guidance.

Description

CVE-2026-76490 is a high-severity vulnerability in Cisco Expressway Series software involving out-of-bounds write issues (CWE-787). Cisco conducted an internal security review leading to software hardening releases addressing multiple vulnerabilities, including this one. The vulnerability can cause a denial of service but does not impact confidentiality or integrity. No public exploits or in-the-wild exploitation have been reported. No specific affected versions or patch details are provided in the available data.

Impact

The vulnerability allows an attacker to cause denial of service via out-of-bounds writes, impacting the availability of the Cisco Expressway Series software. There is no reported impact on confidentiality or integrity. No known exploits are currently active in the wild.

Summary

Cisco Expressway Series software contains multiple internally discovered vulnerabilities related to out-of-bounds writes, tracked under CVE-2026-76490 and CWE-787. These vulnerabilities were identified during a comprehensive internal security review by Cisco's engineering team. The CVSS v3.1 score is 8.6, indicating high severity, with an attack vector of network, low attack complexity, no privileges or user interaction required, and a scope change. The impact is limited to availability (denial of service), with no confidentiality or integrity impact reported. Cisco has released software hardening updates as part of this review, though specific patch versions or links are not provided in the data.

CWE-787Out-of-bounds Write (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #5
The product writes data past the end, or before the beginning, of the intended buffer.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Operation · Build and Compilation · Environment Hardening
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index…
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 7 Nov 2026, 19:47 UTC

WeaknessesCWE-787

Technical details

References

Community reviews

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