Answer in brief
CVE-2026-20301 records a High severity (CVSS 8.6) vulnerability in Cisco IOS Software and IOS XE Software Extensible Messaging Client Protocol Denial of Service Vulnerability. The current sources do not mark it as known exploited. The current feed maps Cisco/Cisco IOS XE Software (generic), Cisco/IOS (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 8.6. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Cisco/Cisco IOS XE Software (generic), Cisco/IOS (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Cisco/Cisco IOS XE Softwaregeneric | 17.2.1a || 16.12.1y || 16.12.3s || 16.7.1b || 16.6.2 || 16.6.5 || 16.12.1w || 16.9.1d || 17.3.1 || 16.9.4c || 16.7.1 || 17.2.1 || 16.6.8 || 16.9.1b || 16.9.2s || 16.12.4 || 16.12.3a || 17.1.1s || 16.11.1a || 16.7.2 || 16.11.1b || 16.9.1s || 16.9.3h || 16.9.1c || 16.6.5a || 16.6.3 || 16.10.1f || 17.2.1v || 16.8.1e || 16.9.3a || 16.12.1a || 16.12.1x || 3.16.10aS || 16.6.4s || 16.10.1c || 16.12.3 || 16.11.2 || 16.6.5b || 16.12.2s || 16.10.1b || 16.7.3 || 16.6.7 || 16.9.6 || 16.9.2 || 16.10.1 || 16.12.1t || 16.9.1 || 16.8.1a || 3.18.8aSP || 16.9.3s || 16.6.7a || 16.12.2 || 16.11.1 || 16.9.3 || 16.11.1s || 16.12.1 || 17.1.1 || 17.1.2 || 16.10.1d || 17.1.1t || 16.9.4 || 16.8.3 || 16.12.2t || 16.9.5 || 16.8.1s || 16.10.1e || 16.8.2 || 16.6.4 || 16.8.1b || 16.10.1a || 16.12.1z || 16.8.1c || 16.9.1a || 16.9.5f || 16.6.4a || 16.10.1g || 16.8.1 || 16.6.6 || 16.9.2a || 16.8.1d || 16.10.3 || 16.7.1a || 16.11.1c || 16.10.1s || 17.2.1r || 17.1.1a || 16.10.2 || 16.12.2a || 16.12.1c || 16.12.1s || 16.7.4 || 3.18.9SP || 17.2.2 || 3.11.3E || 16.9.8 || 16.9.7 || 17.1.3 || 17.3.1a || 3.11.4E || 17.3.2a || 16.12.5 || 17.3.1w || 17.3.2 || 3.11.3aE || 17.4.1 || 16.12.4a || 17.4.1a || 3.16.10bS || 17.3.1x || 17.3.3 || 16.6.9 || 17.2.3 || 17.5.1 || 16.12.1z1 || 16.12.5a || 17.4.1b || 17.3.1z || 16.12.5b || 17.4.2 || 17.3.3a || 3.11.5E || 17.3.5 || 17.3.4 || 17.5.1a || 16.12.6 || 17.6.1 || 16.12.1z2 || 16.6.10 || 17.3.4a || 17.6.1a || 3.8.10cE || 17.7.1 || 17.6.1x || 17.6.2 || 16.12.6a || 17.3.4c || 17.4.2a || 17.3.4b || 17.7.1a || 16.12.7 || 17.8.1a || 17.6.3a || 17.6.3 || 17.7.2 || 17.7.1b || 17.9.1w || 17.3.5a || 17.6.1z || 3.8.10dE || 16.12.8 || 17.8.1 || 17.9.1 || 3.11.6E || 17.6.4 || 3.11.7E || 17.3.5b || 17.9.1a || 17.3.6 || 17.10.1 || 3.11.8E || 16.9.8a || 17.6.1z1 || 17.10.1a || 17.9.2 || 17.6.5 || 17.9.1x || 17.9.1y || 16.9.8b || 17.3.7 || 17.9.2a || 17.9.3 || 16.12.9 || 17.11.1 || 17.10.1b || 17.6.6 || 17.9.1x1 || 17.11.1a || 17.9.3a || 17.12.1 || 17.3.8 || 17.9.4 || 16.12.10 || 17.12.1w || 17.9.1y1 || 17.12.1a || 3.11.9E || 17.9.5 || 17.13.1 || 17.12.1x || 17.12.2 || 17.14.1 || 17.9.4a || 17.3.8a || 17.6.6a || 17.6.5a || 17.6.7 || 16.12.10a || 17.15.1 || 17.13.1a || 17.12.2a || 16.12.11 || 17.12.3 || 17.12.1y || 3.11.10E || 17.12.1z || 17.9.5a || 17.14.1a || 17.9.5b || 17.6.8 || 16.12.12 || 17.12.4 || 17.9.6 || 17.17.1 || 17.16.1 || 17.15.1w || 17.12.3a || 3.11.11E || 17.9.5c || 17.15.1a || 17.12.1z1 || 17.15.2 || 17.15.1b || 17.9.5d || 17.15.1x || 17.9.6a || 17.12.1z2 || 17.6.8a || 17.16.1a || 16.12.13 || 17.15.3 || 17.9.7 || 17.12.5 || 17.15.1y || 17.9.5e || 17.12.4a || 17.15.2a || 17.15.2c || 17.15.2b || 17.12.1z3 || 17.9.5f || 17.12.4b || 3.11.12E || 17.12.5a || 17.18.1 || 17.12.6 || 17.12.1z4 || 17.9.8 || 17.9.7a || 17.15.3a || 17.15.4 || 3.11.13E || 17.12.5b || 17.15.3b || 16.12.14 || 17.18.1z || 17.9.7b || 17.12.5c || 26.1.1 || 17.18.1a || 17.15.4a || 17.18.2 || 17.18.1w || 17.15.4b || 17.12.6a || 17.12.7 || 17.15.4c || 17.9.9 || 17.12.5d || 16.12.15 || 17.15.4s1 || 17.15.5 || 17.12.1z5 || 17.18.1x || 17.12.1z6 || 17.15.4d || 17.12.6b || 17.4.1c || 3.11.14E || 17.15.5a || 17.18.1y || 17.12.7a || 17.18.3 || 17.12.7b || 17.18.3a || 26.1.1a || 26.2.1ea || 16.12.16 | Not reported |
| Cisco/IOSgeneric | 15.2(7)E7 || 15.2(8)E3 || 15.7(3)M10 || 15.8(3)M9 || 15.9(3)M7 || 15.2(7)E8 || 15.2(8)E4 || 15.9(3)M7a || 15.2(2)E10c || 15.2(4)E10d || 15.9(3)M6a || 15.9(3)M6b || 15.5(1)SY10 || 15.5(1)SY11 || 15.2(6)E1a || 15.4(1)SY4 || 15.5(1)SY1 || 15.2(2)E8 || 15.2(6)E1 || 15.7(3)M2 || 15.2(4)E6 || 15.2(1)SY6 || 15.2(4)EA7 || 15.2(6)E1s || 15.7(3)M3 || 15.8(3)M || 15.2(1)SY7 || 15.2(4)EA8 || 15.8(3)M0a || 15.2(2)E9 || 15.2(6)E2 || 15.5(1)SY2 || 15.2(4)E7 || 15.2(6)E2a || 15.2(2)E9a || 15.8(3)M0b || 15.2(6)E2b || 15.8(3)M1 || 15.8(3)M1a || 15.7(3)M4 || 15.2(1)SY8 || 15.2(4)E8 || 15.5(1)SY3 || 15.2(7)E || 15.7(3)M4a || 15.8(3)M2 || 15.2(7)E0a || 15.8(3)M2a || 15.7(3)M4b || 15.2(2)E10 || 15.2(7)E0s || 15.2(4)EA9 || 15.2(7)E0b || 15.2(6)E3 || 15.9(3)M || 15.8(3)M3 || 15.5(1)SY4 || 15.7(3)M5 || 15.2(2)E10a || 15.2(4)E9 || 15.2(7)E1 || 15.8(3)M3b || 15.9(3)M0a || 15.2(7)E1a || 15.2(4)E10 || 15.5(1)SY5 || 15.2(4)EA9a || 15.9(3)M1 || 15.8(3)M4 || 15.7(3)M6 || 15.2(7)E2 || 15.5(1)SY6 || 15.2(7)E3 || 15.8(3)M5 || 15.7(3)M7 || 15.9(3)M2 || 15.2(7)E2b || 15.9(3)M2a || 15.2(4)E10a || 15.2(7)E4 || 15.5(1)SY7 || 15.2(4)E10b || 15.2(7)E3k || 15.2(8)E || 15.9(3)M3 || 15.8(3)M6 || 15.7(3)M8 || 15.8(3)M7 || 15.5(1)SY8 || 15.2(7)E5 || 15.2(8)E1 || 15.9(3)M4 || 15.2(8)E2 || 15.2(4)E10c || 15.7(3)M9 || 15.2(2)E10b || 15.2(7)E6 || 15.9(3)M4a || 15.5(1)SY9 || 15.9(3)M5 || 15.8(3)M8 || 15.9(3)M6 || 15.9(3)M9 || 15.5(1)SY13 || 15.9(3)M8b || 15.2(7)E9 || 15.5(1)SY12 || 15.7(3)M10a || 15.9(3)M8 || 15.9(3)M8a || 15.2(8)E5 || 15.2(7)E10 || 15.7(3)M10b || 15.9(3)M3a || 15.8(3)M3a || 15.9(3)M3b || 15.6(2)SP7 || 15.6(2)SP5 || 15.6(2)SP8 || 15.6(2)SP6 || 15.6(2)SP4 || 15.6(2)SP9 || 15.6(2)SP8a || 15.9(3)M9a || 15.2(8)E6 || 15.9(3)M10 || 15.2(7)E11 || 15.5(1)SY14 || 15.2(8)E7 || 15.2(4)E10e || 15.9(3)M11 || 15.2(7)E12 || 15.5(1)SY15 || 15.2(8)E8 || 15.5(1)SY16 || 15.2(7)E13 || 15.9(3)M12 || 15.5(1)SY17 || 15.2(7)E14 || 15.9(3)M13 | Not reported |
Published upstream
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
A vulnerability in the Extensible Messaging Client Protocol (XMCP), also referred to as the External Client protocol, of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper handling of malformed XMCP packets. An attacker could exploit this vulnerability by sending a malformed XMCP packet to an affected device. A successful exploit could allow the attacker to cause the affected device to reload unexpectedly, resulting in a DoS condition. The attacker does not need the XMCP client username to exploit this vulnerability.
Quoted source text, attributed separately from HOL analysis.
Answer in brief
CVE-2026-20301 records a High severity (CVSS 8.6) vulnerability in Cisco IOS Software and IOS XE Software Extensible Messaging Client Protocol Denial of Service Vulnerability. The current sources do not mark it as known exploited. The current feed maps Cisco/Cisco IOS XE Software (generic), Cisco/IOS (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 8.6. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Cisco/Cisco IOS XE Software (generic), Cisco/IOS (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Cisco/Cisco IOS XE Softwaregeneric | 17.2.1a || 16.12.1y || 16.12.3s || 16.7.1b || 16.6.2 || 16.6.5 || 16.12.1w || 16.9.1d || 17.3.1 || 16.9.4c || 16.7.1 || 17.2.1 || 16.6.8 || 16.9.1b || 16.9.2s || 16.12.4 || 16.12.3a || 17.1.1s || 16.11.1a || 16.7.2 || 16.11.1b || 16.9.1s || 16.9.3h || 16.9.1c || 16.6.5a || 16.6.3 || 16.10.1f || 17.2.1v || 16.8.1e || 16.9.3a || 16.12.1a || 16.12.1x || 3.16.10aS || 16.6.4s || 16.10.1c || 16.12.3 || 16.11.2 || 16.6.5b || 16.12.2s || 16.10.1b || 16.7.3 || 16.6.7 || 16.9.6 || 16.9.2 || 16.10.1 || 16.12.1t || 16.9.1 || 16.8.1a || 3.18.8aSP || 16.9.3s || 16.6.7a || 16.12.2 || 16.11.1 || 16.9.3 || 16.11.1s || 16.12.1 || 17.1.1 || 17.1.2 || 16.10.1d || 17.1.1t || 16.9.4 || 16.8.3 || 16.12.2t || 16.9.5 || 16.8.1s || 16.10.1e || 16.8.2 || 16.6.4 || 16.8.1b || 16.10.1a || 16.12.1z || 16.8.1c || 16.9.1a || 16.9.5f || 16.6.4a || 16.10.1g || 16.8.1 || 16.6.6 || 16.9.2a || 16.8.1d || 16.10.3 || 16.7.1a || 16.11.1c || 16.10.1s || 17.2.1r || 17.1.1a || 16.10.2 || 16.12.2a || 16.12.1c || 16.12.1s || 16.7.4 || 3.18.9SP || 17.2.2 || 3.11.3E || 16.9.8 || 16.9.7 || 17.1.3 || 17.3.1a || 3.11.4E || 17.3.2a || 16.12.5 || 17.3.1w || 17.3.2 || 3.11.3aE || 17.4.1 || 16.12.4a || 17.4.1a || 3.16.10bS || 17.3.1x || 17.3.3 || 16.6.9 || 17.2.3 || 17.5.1 || 16.12.1z1 || 16.12.5a || 17.4.1b || 17.3.1z || 16.12.5b || 17.4.2 || 17.3.3a || 3.11.5E || 17.3.5 || 17.3.4 || 17.5.1a || 16.12.6 || 17.6.1 || 16.12.1z2 || 16.6.10 || 17.3.4a || 17.6.1a || 3.8.10cE || 17.7.1 || 17.6.1x || 17.6.2 || 16.12.6a || 17.3.4c || 17.4.2a || 17.3.4b || 17.7.1a || 16.12.7 || 17.8.1a || 17.6.3a || 17.6.3 || 17.7.2 || 17.7.1b || 17.9.1w || 17.3.5a || 17.6.1z || 3.8.10dE || 16.12.8 || 17.8.1 || 17.9.1 || 3.11.6E || 17.6.4 || 3.11.7E || 17.3.5b || 17.9.1a || 17.3.6 || 17.10.1 || 3.11.8E || 16.9.8a || 17.6.1z1 || 17.10.1a || 17.9.2 || 17.6.5 || 17.9.1x || 17.9.1y || 16.9.8b || 17.3.7 || 17.9.2a || 17.9.3 || 16.12.9 || 17.11.1 || 17.10.1b || 17.6.6 || 17.9.1x1 || 17.11.1a || 17.9.3a || 17.12.1 || 17.3.8 || 17.9.4 || 16.12.10 || 17.12.1w || 17.9.1y1 || 17.12.1a || 3.11.9E || 17.9.5 || 17.13.1 || 17.12.1x || 17.12.2 || 17.14.1 || 17.9.4a || 17.3.8a || 17.6.6a || 17.6.5a || 17.6.7 || 16.12.10a || 17.15.1 || 17.13.1a || 17.12.2a || 16.12.11 || 17.12.3 || 17.12.1y || 3.11.10E || 17.12.1z || 17.9.5a || 17.14.1a || 17.9.5b || 17.6.8 || 16.12.12 || 17.12.4 || 17.9.6 || 17.17.1 || 17.16.1 || 17.15.1w || 17.12.3a || 3.11.11E || 17.9.5c || 17.15.1a || 17.12.1z1 || 17.15.2 || 17.15.1b || 17.9.5d || 17.15.1x || 17.9.6a || 17.12.1z2 || 17.6.8a || 17.16.1a || 16.12.13 || 17.15.3 || 17.9.7 || 17.12.5 || 17.15.1y || 17.9.5e || 17.12.4a || 17.15.2a || 17.15.2c || 17.15.2b || 17.12.1z3 || 17.9.5f || 17.12.4b || 3.11.12E || 17.12.5a || 17.18.1 || 17.12.6 || 17.12.1z4 || 17.9.8 || 17.9.7a || 17.15.3a || 17.15.4 || 3.11.13E || 17.12.5b || 17.15.3b || 16.12.14 || 17.18.1z || 17.9.7b || 17.12.5c || 26.1.1 || 17.18.1a || 17.15.4a || 17.18.2 || 17.18.1w || 17.15.4b || 17.12.6a || 17.12.7 || 17.15.4c || 17.9.9 || 17.12.5d || 16.12.15 || 17.15.4s1 || 17.15.5 || 17.12.1z5 || 17.18.1x || 17.12.1z6 || 17.15.4d || 17.12.6b || 17.4.1c || 3.11.14E || 17.15.5a || 17.18.1y || 17.12.7a || 17.18.3 || 17.12.7b || 17.18.3a || 26.1.1a || 26.2.1ea || 16.12.16 | Not reported |
| Cisco/IOSgeneric | 15.2(7)E7 || 15.2(8)E3 || 15.7(3)M10 || 15.8(3)M9 || 15.9(3)M7 || 15.2(7)E8 || 15.2(8)E4 || 15.9(3)M7a || 15.2(2)E10c || 15.2(4)E10d || 15.9(3)M6a || 15.9(3)M6b || 15.5(1)SY10 || 15.5(1)SY11 || 15.2(6)E1a || 15.4(1)SY4 || 15.5(1)SY1 || 15.2(2)E8 || 15.2(6)E1 || 15.7(3)M2 || 15.2(4)E6 || 15.2(1)SY6 || 15.2(4)EA7 || 15.2(6)E1s || 15.7(3)M3 || 15.8(3)M || 15.2(1)SY7 || 15.2(4)EA8 || 15.8(3)M0a || 15.2(2)E9 || 15.2(6)E2 || 15.5(1)SY2 || 15.2(4)E7 || 15.2(6)E2a || 15.2(2)E9a || 15.8(3)M0b || 15.2(6)E2b || 15.8(3)M1 || 15.8(3)M1a || 15.7(3)M4 || 15.2(1)SY8 || 15.2(4)E8 || 15.5(1)SY3 || 15.2(7)E || 15.7(3)M4a || 15.8(3)M2 || 15.2(7)E0a || 15.8(3)M2a || 15.7(3)M4b || 15.2(2)E10 || 15.2(7)E0s || 15.2(4)EA9 || 15.2(7)E0b || 15.2(6)E3 || 15.9(3)M || 15.8(3)M3 || 15.5(1)SY4 || 15.7(3)M5 || 15.2(2)E10a || 15.2(4)E9 || 15.2(7)E1 || 15.8(3)M3b || 15.9(3)M0a || 15.2(7)E1a || 15.2(4)E10 || 15.5(1)SY5 || 15.2(4)EA9a || 15.9(3)M1 || 15.8(3)M4 || 15.7(3)M6 || 15.2(7)E2 || 15.5(1)SY6 || 15.2(7)E3 || 15.8(3)M5 || 15.7(3)M7 || 15.9(3)M2 || 15.2(7)E2b || 15.9(3)M2a || 15.2(4)E10a || 15.2(7)E4 || 15.5(1)SY7 || 15.2(4)E10b || 15.2(7)E3k || 15.2(8)E || 15.9(3)M3 || 15.8(3)M6 || 15.7(3)M8 || 15.8(3)M7 || 15.5(1)SY8 || 15.2(7)E5 || 15.2(8)E1 || 15.9(3)M4 || 15.2(8)E2 || 15.2(4)E10c || 15.7(3)M9 || 15.2(2)E10b || 15.2(7)E6 || 15.9(3)M4a || 15.5(1)SY9 || 15.9(3)M5 || 15.8(3)M8 || 15.9(3)M6 || 15.9(3)M9 || 15.5(1)SY13 || 15.9(3)M8b || 15.2(7)E9 || 15.5(1)SY12 || 15.7(3)M10a || 15.9(3)M8 || 15.9(3)M8a || 15.2(8)E5 || 15.2(7)E10 || 15.7(3)M10b || 15.9(3)M3a || 15.8(3)M3a || 15.9(3)M3b || 15.6(2)SP7 || 15.6(2)SP5 || 15.6(2)SP8 || 15.6(2)SP6 || 15.6(2)SP4 || 15.6(2)SP9 || 15.6(2)SP8a || 15.9(3)M9a || 15.2(8)E6 || 15.9(3)M10 || 15.2(7)E11 || 15.5(1)SY14 || 15.2(8)E7 || 15.2(4)E10e || 15.9(3)M11 || 15.2(7)E12 || 15.5(1)SY15 || 15.2(8)E8 || 15.5(1)SY16 || 15.2(7)E13 || 15.9(3)M12 || 15.5(1)SY17 || 15.2(7)E14 || 15.9(3)M13 | Not reported |
Published upstream
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
A vulnerability in the Extensible Messaging Client Protocol (XMCP), also referred to as the External Client protocol, of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper handling of malformed XMCP packets. An attacker could exploit this vulnerability by sending a malformed XMCP packet to an affected device. A successful exploit could allow the attacker to cause the affected device to reload unexpectedly, resulting in a DoS condition. The attacker does not need the XMCP client username to exploit this vulnerability.
Quoted source text, attributed separately from HOL analysis.