Adaptive Security Appliance SoftwareApplication · Cisco
CVE-2013-5557
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 Proxy Bypass Content Rewriter feature in the WebVPN subsystem in Cisco Adaptive Security Appliance (ASA) Software 9.1(.2) and earlier allows remote authenticated users to cause a denial of service (device crash or error-recovery event) via an HTTP request that triggers a rewrite, aka Bug ID CSCug91577.
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 confidenceA denial of service vulnerability exists in the Proxy Bypass Content Rewriter of Cisco ASA WebVPN. Authenticated remote users can trigger a crash or error-recovery event by sending specially crafted HTTP requests that cause the rewriter to fail.
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
Adaptive Security Appliance SoftwareApplication
<= 9.1\(2\)CVSS 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 Cisco ASA device and versionAccess the ASA CLI and run the command 'show version' to display the installed software version. Alternatively, check via ASDM under Device Dashboard > Device Information.Affected if The displayed Cisco ASA Software version is 9.1(2) or any earlier version.
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Confirm WebVPN is enabledRun 'show webvpn' in ASA CLI or check via ASDM under Configuration > Remote Access VPN > WebVPN. Look for WebVPN enable status.Affected if WebVPN is enabled and active on the device.
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Verify Proxy Bypass configuration existsRun 'show run webvpn' or 'show run webvpn transform' to view WebVPN configuration. Look for 'proxy-bypass' or 'proxy bypass' entries in the configuration.Affected if Proxy Bypass feature is explicitly configured in the WebVPN settings.
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Check current WebVPN session activityRun 'show webvpn session' to display active WebVPN sessions. Note if authenticated users are connected via WebVPN.Affected if Authenticated WebVPN users are active or permitted to connect.
A user is affected if running Cisco ASA Software version 9.1(2) or lower, WebVPN is enabled, and Proxy Bypass feature is configured, allowing authenticated remote users to trigger the denial of service.
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 dataUpgrade Cisco ASA Software to a version later than 9.1(2). If immediate upgrade is not possible, consider restricting WebVPN access to trusted users only through access lists or disabling the Proxy Bypass feature if not required.
Fix this in Adaptive Security Appliance Software
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2013-5557 — 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-2013-5557 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
- No weaponised exploit code, or anything meant to cause harm
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