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Big Ip Access Policy ManagerApplication · F5

CVE-2021-23049

HIGH · 7.5 CVSS v3.1 Published 2021-09-14
Fix available
A fix is available. Upgrade to 15.1.3 / 16.0.1.2 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

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 · unedited
On BIG-IP version 16.0.x before 16.0.1.2 and 15.1.x before 15.1.3, when the iRules RESOLVER::summarize command is used on a virtual server, undisclosed requests can cause an increase in Traffic Management Microkernel (TMM) memory utilization resulting in an out-of-memory condition and a denial-of-service (DoS). Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

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 confidence

A denial-of-service vulnerability exists in F5 BIG-IP's Traffic Management Microkernel (TMM) when the iRules RESOLVER::summarize command is used on a virtual server. Undisclosed requests trigger excessive memory utilization that can lead to an out-of-memory condition, causing the TMM to fail.

MitigationUpgrade BIG-IP to version 16.0.1.2 or later (for 16.0.x) or 15.1.3 or later (for 15.1.x). If upgrading is not immediately feasible, review and restrict access to virtual servers using the RESOLVER::summarize iRule command.

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
Big Ip Access Policy ManagerApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.2
Big Ip Advanced Firewall ManagerApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.2
Big Ip Advanced Web Application FirewallApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.2
Big Ip AnalyticsApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.2
Big Ip Application Acceleration ManagerApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.2
Big Ip Application Security ManagerApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.2
Big Ip Domain Name SystemApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.2
Big Ip Fraud Protection ServiceApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.2

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
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the BIG-IP version
    Run the command 'tmsh show sys version' or check the BIG-IP web UI under System > Software Management > Software List to view the installed version.
    Affected if The installed version is 15.1.0 through 15.1.2.x, or 16.0.0 through 16.0.1.1, meaning it falls within the ranges >= 15.1.0, < 15.1.3 or >= 16.0.0, < 16.0.1.2.
  2. Locate iRules using the RESOLVER::summarize command
    Run 'tmsh list ltm rule all' to list all iRules, then search for the string 'RESOLVER::summarize' within the output using grep or manual inspection.
    Affected if Any iRule contains the RESOLVER::summarize command, indicating this specific iRule command is in use.
  3. Identify virtual servers with vulnerable iRules attached
    Run 'tmsh list ltm virtual' to list all virtual servers and their associated iRules, then cross-reference with the iRules found in the previous step.
    Affected if A virtual server has an iRule containing RESOLVER::summarize attached to it, meaning the vulnerable code path can be triggered by traffic to that virtual server.
  4. Verify TMM memory utilization
    Check the Traffic Management Microkernel status via 'tmsh show sys tmm-info' or monitor /var/log/ltm for out-of-memory messages related to TMM.
    Affected if TMM is experiencing abnormally high memory usage or has encountered out-of-memory conditions, which could indicate exploitation of this vulnerability.

You are affected if your BIG-IP version is 15.1.0-15.1.2.x or 16.0.0-16.0.1.1 AND you have iRules containing the RESOLVER::summarize command attached to virtual servers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Upgrade available Upgrade to 15.1.3 / 16.0.1.2 or later
Fixed in 15.1.316.0.1.2
Interim mitigation

Upgrade BIG-IP to version 16.0.1.2 or later (for 16.0.x) or 15.1.3 or later (for 15.1.x). If upgrading is not immediately feasible, review and restrict access to virtual servers using the RESOLVER::summarize iRule command.

Recommended fix High confidence

BIG-IP 15.1.3 or 16.0.1.2 (depending on current branch)

  1. 1. Back up the BIG-IP configuration using 'tmsh save sys config' or the configuration utility.
  2. 2. Download the fixed BIG-IP version (15.1.3 for 15.1.x branch or 16.0.1.2 for 16.0.x branch) from the F5 Networks download site (downloads.f5.com).
  3. 3. Upload the ISO image to the BIG-IP device via the configuration utility or SCP.
  4. 4. Verify the image integrity using the provided checksum/md5sum.
  5. 5. Install the software upgrade using the configuration utility (System > Software Management > ISO Image > Install) or via TMSH: 'tmsh install sys software volume <volume-name> create-only volume <volume-name> image <image-name>'.
  6. 6. Activate the new volume using TMSH: 'tmsh activate sys volume <volume-name>'.
  7. 7. After the system reboots, verify the upgrade was successful and the new version is running: 'tmsh show sys version'.
  8. 8. Test the iRules functionality to ensure the RESOLVER::summarize command no longer causes memory issues.
Caveat Standard BIG-IP upgrade considerations apply - review release notes for any behavioral changes, ensure compatible iRules syntax, and plan for maintenance window as upgrade requires reboot.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Big Ip Access Policy Manager Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-23049 in production — separate from our analysis above.

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