VulnerabilityPublished 15 Oct 2025

CVE-2025-20351: Cisco Session Initiation Protocol (SIP) Software · Cross-site Scripting

Affects Cisco Session Initiation Protocol (SIP) SoftwareSource CVE Database V5

Not known to be exploited · CVSS 6.1 Medium.

Data as of 26 Oct 2026, 10:12 UTC

CVSS 3.1 base score

6.1Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 21% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

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

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: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 15 Oct 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 Oct 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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.

What to do

Affected software

Product	Affected	Fixed in
Cisco Cisco Session Initiation Protocol (SIP) Software	Affected 2.0 – 14.3 23 affected builds	Fixed in–

AI-suggested

Immediately verify if Web Access is enabled on Cisco SIP phones; disable it if remote web management is not essential, as it is disabled by default and disabling it removes the attack vector.
Monitor Cisco’s security advisories closely for patches or firmware updates addressing CVE-2025-20351 and apply them promptly once available.
Implement strict network segmentation to isolate SIP devices from general user networks and restrict access to their management interfaces to trusted administrators only.
Employ web application firewalls (WAFs) or intrusion prevention systems (IPS) capable of detecting and blocking XSS payloads targeting device web UIs.
Educate users about the risks of clicking unsolicited or suspicious links, especially those related to device management interfaces.
Audit and harden unified communications infrastructure configurations, ensuring minimal exposure of management interfaces to external or untrusted networks.
Enable logging and continuous monitoring of SIP device web UI access to detect anomalous activities indicative of exploitation attempts.
Consider deploying endpoint protection solutions that can detect script injection or unusual browser behaviors when accessing device web UIs.

Description

A vulnerability in the web UI of Cisco Desk Phone 9800 Series, Cisco IP Phone 7800 and 8800 Series, and Cisco Video Phone 8875 running Cisco SIP Software could allow an unauthenticated, remote attacker to conduct XSS attacks against a user of the web UI. This vulnerability exists because the web UI of an affected device does not sufficiently validate user-supplied input. An attacker could exploit this vulnerability by persuading a user to click a crafted link. A successful exploit could allow the attacker to execute arbitrary script code in the context of the affected interface or access sensitive, browser-based information. Note: To exploit this vulnerability, the phone must be registered to Cisco Unified Communications Manager and have Web Access enabled. Web Access is disabled by default.

Impact

For European organizations, this vulnerability poses a risk to the confidentiality and integrity of communications managed via Cisco SIP-enabled phones. Exploitation could allow attackers to steal sensitive information accessible through the phone’s web UI or hijack user sessions, potentially leading to further compromise of unified communications infrastructure. Organizations in sectors with high reliance on secure voice and video communications—such as government, finance, healthcare, and critical infrastructure—may face increased risk. The requirement for user interaction and Web Access being disabled by default somewhat limits the attack surface, but environments that enable Web Access for remote management are vulnerable. Successful exploitation could facilitate espionage, data leakage, or lateral movement within corporate networks. Additionally, compromised devices could be used as footholds for launching further attacks against internal systems. The broad range of affected software versions indicates many deployed devices may be vulnerable, especially in large enterprises and public sector organizations across Europe. The lack of known exploits reduces immediate urgency but does not eliminate the threat, as attackers may develop exploits once details become widely known.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-phone-dos-FPyjLV7A (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 15 Oct 2025, 16:40 UTC

Technical details

References

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