CVE-2025-20350VulnerabilityPublished 15 Oct 2025

CVE-2025-20350: Cisco Session Initiation Protocol (SIP) Software · Stack-based Buffer Overflow

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

Not known to be exploited · CVSS 7.5 High.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 40% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
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: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
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 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 2026-10-25.

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 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 =11.5 =10.3 =10.2 =11.0 =11.7 =12.1 =12.5 =12.6 =12.0 =9.3 =12.7 =12.8 =14.0 =14.1 =14.2 =3.1 =3.0 =2.3 =2.2 =2.1 =2.0 =14.3 =3.2	Fixed in–

AI-suggested

1. Immediately verify if Web Access is enabled on any Cisco IP phones running affected SIP software versions; disable Web Access if it is not required, as it is disabled by default and disabling it removes the attack vector. 2. Restrict network access to the management interfaces of affected devices by implementing strict firewall rules and network segmentation to limit exposure to trusted administrative hosts only. 3. Monitor Cisco security advisories closely for the release of official patches or firmware updates addressing CVE-2025-20350 and plan for rapid deployment once available. 4. Conduct internal audits to identify all affected Cisco IP phones and their software versions to prioritize remediation efforts. 5. Employ intrusion detection/prevention systems (IDS/IPS) with updated signatures to detect and block attempts to exploit this vulnerability by monitoring for anomalous HTTP traffic targeting the phones. 6. Educate IT and security teams about this vulnerability to ensure awareness and readiness to respond to any incidents. 7. Consider isolating voice infrastructure from general corporate networks to reduce the attack surface. 8. Regularly back up configuration and maintain incident response plans specific to telephony infrastructure disruptions.

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 cause a DoS condition on an affected device. This vulnerability is due to a buffer overflow when an affected device processes HTTP packets. An attacker could exploit this vulnerability by sending crafted HTTP input to the device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition. 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, the primary impact of CVE-2025-20350 is the potential disruption of voice communication services due to denial-of-service conditions on affected Cisco IP phones. Many enterprises, government agencies, and critical infrastructure operators in Europe rely heavily on Cisco telephony solutions for internal and external communications. A successful exploit could cause phones to reload unexpectedly, interrupting calls and potentially degrading business operations, emergency response, and customer service. This could be particularly damaging in sectors such as finance, healthcare, public administration, and telecommunications, where reliable voice communication is essential. Additionally, widespread exploitation could lead to reputational damage and operational delays. Although the vulnerability does not allow data theft or device takeover, the availability impact alone can have significant operational consequences. The requirement that phones be registered to Cisco Unified Communications Manager and have Web Access enabled somewhat limits exposure, but organizations with these configurations remain at risk. Attackers could target exposed management interfaces from the internet or internal networks if proper segmentation and access controls are not in place. The lack of known exploits currently provides a window for proactive mitigation, but the ease of exploitation and high severity score indicate that rapid action is necessary to prevent future incidents.

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, 16:38 UTC

Technical details

References

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