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Cisco Bug: CSCvt84618 - ISR Router Running 15.6M or 15.7M Experiences Memory Corruption Crashes with WebVPN

Last Modified

Jun 03, 2020

Products (1)

  • Cisco 3900 Series Integrated Services Routers

Known Affected Releases

15.7(3.0b)M4

Description (partial)

Symptom:
An ISR G2 ("generation 2") router (eg: 19xx, 29xx, 39xx) running IOS 15.6M or 15.7M code may experience crashes related to memory corruption in various features associated with a WebVPN configuration. Impacted processes may include IKEv2, SSLVPN, and HTTP. 

One sign of this issue is that the "refcount" counter for the memory block of an impacted process has experienced a counter underflow event such that it has decremented from "0" to "FFFFFFFF". Examples:

SYS-2-CHUNKBADREFCOUNT: Bad chunk reference count, chunk XXXXXXXX data XXXXXXXX refcount FFFFFFFF alloc pc XXX. -Process= "Crypto IKEv2", ipl= 0, pid= XXX

SYS-2-CHUNKBADREFCOUNT: Bad chunk reference count, chunk XXXXXXXX data XXXXXXXX refcount FFFFFFFF alloc pc XXX. -Process= "SSLVPN_PROCESS", ipl= 0, pid= XXX

SYS-2-CHUNKBADREFCOUNT: Bad chunk reference count, chunk XXXXXXXX data XXXXXXXX refcount FFFFFFFF alloc pc XXX. -Process= "HTTP CORE", ipl= 0, pid= XXX

Conditions:
- Router is running IOS 15.6M or 15.7M code. IOS 15.5M and earlier may not be impacted.
- WebVPN is enabled with HTTPS sessions terminating on the device
- "ip http secure-server" may need to be configured. This is unconfirmed. This should not normally be configured if WebVPN is also enabled. See:
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/sec_conn_sslvpn/configuration/15-mt/sec-conn-sslvpn-15-mt-book/sec-conn-sslvpn-ssl-vpn.html
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