iOSOperating system · Cisco
CVE-2013-1241
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedThe ISM module in Cisco IOS on ISR G2 routers does not properly handle authentication-header packets, which allows remote authenticated users to cause a denial of service (module reload) via a series of malformed packets, aka Bug ID CSCub92025.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe ISM (IP Security) module in Cisco IOS on ISR G2 routers fails to properly handle malformed authentication-header (AH) packets. When a remote authenticated attacker sends specially crafted AH packets, the module reloads, causing denial of service. The attack requires valid authentication credentials.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
iOSOperating system
all versions
1921 Integrated Services RouterHardware / appliance
all versions
1941 Integrated Services RouterHardware / appliance
all versions
1941w Integrated Services RouterHardware / appliance
all versions
2901 Integrated Services RouterHardware / appliance
all versions
2911 Integrated Services RouterHardware / appliance
all versions
2921 Integrated Services RouterHardware / appliance
all versions
2951 Integrated Services RouterHardware / appliance
all versionsCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- M
- Authentication
- Single
- Confidentiality
- None
- Integrity
- None
- Availability
- Complete
AV:N/AC:M/Au:S/C:N/I:N/A:C
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify the router modelRun 'show version' or 'show inventory' to confirm the hardware modelAffected if The device is a Cisco 1921, 1941, 1941w, 2901, 2911, 2921, or 2951 Integrated Services Router (ISR G2)
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Check the Cisco IOS versionRun 'show version' to display the installed IOS versionAffected if The device is an affected ISR G2 model running any IOS version (all versions are vulnerable)
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Verify if ISM/IPSec is configuredRun 'show crypto ipsec sa' or 'show crypto isakmp sa' to check for active IPSec security associationsAffected if ISM/IPSec is actively configured and running on the device (the vulnerability requires ISM to be enabled for the attack to apply)
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Check for ISM module reloadsRun 'show logging' or 'show tech-support' and look for ISM reload messages or crashinfoAffected if Recent unexpected ISM module reloads are present in logs without an obvious cause
A user is affected if they are running Cisco IOS on an ISR G2 router (1921/1941/2901/2911/2921/2951) with ISM/IPSec enabled, as all versions of IOS on these platforms are vulnerable to malformed AH packet-induced reloads.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataApply the Cisco IOS fix for Bug ID CSCub92025. Upgrade to a Cisco IOS version that includes the remediation. If immediate patching is not possible, consider network segmentation to limit exposure to authenticated remote attackers and monitor for unusual ISM module reloads.
Fix this in iOS
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,880.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2013-1241 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2013-1241 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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