CVE-2025-20183 [Medium] | Input Validation Bypass in Asyncos

A vulnerability in a policy-based Cisco Application Visibility and Control (AVC) implementation of Cisco AsyncOS Software for Cisco Secure Web Appliance could allow an unauthenticated, remote attacker to evade the antivirus scanner and download a malicious file onto an endpoint.  The vulnerability is due to improper handling of a crafted range request header. An attacker could exploit this vulnerability by sending an HTTP request with a crafted range request header through the affected device. A successful exploit could allow the attacker to evade the antivirus scanner and download malware onto the endpoint without detection by Cisco Secure Web Appliance.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-04-05	0.62%	0.29%	-0.33%
2	2026-03-17	0.53%	0.62%	+0.09%
3	2026-03-16	—	0.53%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-04-05

0.62%

0.29%

-0.33%

2026-03-17

0.53%

0.62%

+0.09%

2026-03-16

—

0.53%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.8	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:N) Service keeps running; no real outage angle.	3.9	1.4	[email protected]
5.3	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:N) Service keeps running; no real outage angle.	3.9	1.4	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.8

3.1

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C): Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N): Service keeps running; no real outage angle.

3.9

1.4

[email protected]

5.3

3.1

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N): Service keeps running; no real outage angle.

3.9

1.4

[email protected]

Affected software / configurations for CVE-2025-20183

Vendor	Product	Version	Raw CPE
cisco	asyncos	11.8.0-414	cpe:2.3:o:cisco:asyncos:11.8.0-414:::::::*
cisco	asyncos	11.8.0-429	cpe:2.3:o:cisco:asyncos:11.8.0-429:::::::*
cisco	asyncos	11.8.0-453	cpe:2.3:o:cisco:asyncos:11.8.0-453:::::::*
cisco	asyncos	11.8.1-023	cpe:2.3:o:cisco:asyncos:11.8.1-023:::::::*
cisco	asyncos	11.8.3-018	cpe:2.3:o:cisco:asyncos:11.8.3-018:::::::*
cisco	asyncos	11.8.3-021	cpe:2.3:o:cisco:asyncos:11.8.3-021:::::::*
cisco	asyncos	11.8.4-004	cpe:2.3:o:cisco:asyncos:11.8.4-004:::::::*
cisco	asyncos	12.0.1-268	cpe:2.3:o:cisco:asyncos:12.0.1-268:::::::*
cisco	asyncos	12.0.1-334	cpe:2.3:o:cisco:asyncos:12.0.1-334:::::::*
cisco	asyncos	12.0.2-004	cpe:2.3:o:cisco:asyncos:12.0.2-004:::::::*
cisco	asyncos	12.0.2-012	cpe:2.3:o:cisco:asyncos:12.0.2-012:::::::*
cisco	asyncos	12.0.3-005	cpe:2.3:o:cisco:asyncos:12.0.3-005:::::::*
cisco	asyncos	12.0.3-007	cpe:2.3:o:cisco:asyncos:12.0.3-007:::::::*
cisco	asyncos	12.0.4-002	cpe:2.3:o:cisco:asyncos:12.0.4-002:::::::*
cisco	asyncos	12.0.5-011	cpe:2.3:o:cisco:asyncos:12.0.5-011:::::::*
cisco	asyncos	12.5.1-011	cpe:2.3:o:cisco:asyncos:12.5.1-011:::::::*
cisco	asyncos	12.5.1-043	cpe:2.3:o:cisco:asyncos:12.5.1-043:::::::*
cisco	asyncos	12.5.2-007	cpe:2.3:o:cisco:asyncos:12.5.2-007:::::::*
cisco	asyncos	12.5.2-011	cpe:2.3:o:cisco:asyncos:12.5.2-011:::::::*
cisco	asyncos	12.5.3-002	cpe:2.3:o:cisco:asyncos:12.5.3-002:::::::*
cisco	asyncos	12.5.4-005	cpe:2.3:o:cisco:asyncos:12.5.4-005:::::::*
cisco	asyncos	12.5.4-011	cpe:2.3:o:cisco:asyncos:12.5.4-011:::::::*
cisco	asyncos	12.5.5-004	cpe:2.3:o:cisco:asyncos:12.5.5-004:::::::*
cisco	asyncos	12.5.5-005	cpe:2.3:o:cisco:asyncos:12.5.5-005:::::::*
cisco	asyncos	12.5.5-008	cpe:2.3:o:cisco:asyncos:12.5.5-008:::::::*
cisco	asyncos	12.5.6-008	cpe:2.3:o:cisco:asyncos:12.5.6-008:::::::*
cisco	asyncos	14.0.1-014	cpe:2.3:o:cisco:asyncos:14.0.1-014:::::::*
cisco	asyncos	14.0.1-040	cpe:2.3:o:cisco:asyncos:14.0.1-040:::::::*
cisco	asyncos	14.0.1-053	cpe:2.3:o:cisco:asyncos:14.0.1-053:::::::*
cisco	asyncos	14.0.1-503	cpe:2.3:o:cisco:asyncos:14.0.1-503:::::::*
cisco	asyncos	14.0.2-012	cpe:2.3:o:cisco:asyncos:14.0.2-012:::::::*
cisco	asyncos	14.0.3-014	cpe:2.3:o:cisco:asyncos:14.0.3-014:::::::*
cisco	asyncos	14.0.4-005	cpe:2.3:o:cisco:asyncos:14.0.4-005:::::::*
cisco	asyncos	14.0.5-007	cpe:2.3:o:cisco:asyncos:14.0.5-007:::::::*
cisco	asyncos	14.1.0-032	cpe:2.3:o:cisco:asyncos:14.1.0-032:::::::*
cisco	asyncos	14.1.0-041	cpe:2.3:o:cisco:asyncos:14.1.0-041:::::::*
cisco	asyncos	14.1.0-047	cpe:2.3:o:cisco:asyncos:14.1.0-047:::::::*
cisco	asyncos	14.5.0-498	cpe:2.3:o:cisco:asyncos:14.5.0-498:::::::*
cisco	asyncos	14.5.0-537	cpe:2.3:o:cisco:asyncos:14.5.0-537:::::::*
cisco	asyncos	14.5.0-673	cpe:2.3:o:cisco:asyncos:14.5.0-673:::::::*
cisco	asyncos	14.5.1-008	cpe:2.3:o:cisco:asyncos:14.5.1-008:::::::*
cisco	asyncos	14.5.1-016	cpe:2.3:o:cisco:asyncos:14.5.1-016:::::::*
cisco	asyncos	14.5.1-510	cpe:2.3:o:cisco:asyncos:14.5.1-510:::::::*
cisco	asyncos	14.5.1-607	cpe:2.3:o:cisco:asyncos:14.5.1-607:::::::*
cisco	asyncos	14.5.2-011	cpe:2.3:o:cisco:asyncos:14.5.2-011:::::::*
cisco	asyncos	14.5.3-033	cpe:2.3:o:cisco:asyncos:14.5.3-033:::::::*
cisco	asyncos	15.0.0-322	cpe:2.3:o:cisco:asyncos:15.0.0-322:::::::*
cisco	asyncos	15.0.0-355	cpe:2.3:o:cisco:asyncos:15.0.0-355:::::::*
cisco	asyncos	15.1.0-287	cpe:2.3:o:cisco:asyncos:15.1.0-287:::::::*
cisco	asyncos	15.2.0-116	cpe:2.3:o:cisco:asyncos:15.2.0-116:::::::*
cisco	asyncos	15.2.0-164	cpe:2.3:o:cisco:asyncos:15.2.0-164:::::::*

References for CVE-2025-20183

URL	Tags
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-swa-range-bypass-2BsEHYSu	Vendor Advisory

URL

CVE-2025-20183 | Cisco Secure Web Appliance Range Request Bypass Vulnerability

Exploit prediction scoring system (EPSS) score for CVE-2025-20183

Common vulnerability scoring system (CVSS) metrics for CVE-2025-20183

Weakness enumeration for CVE-2025-20183

Affected software / configurations for CVE-2025-20183

References for CVE-2025-20183