Evidence used
- No CISA KEV confirmation is currently recorded.
- The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
- EPSS is 67.64% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2021
CVE-2021-22992High confidence
n/a BIG-IP Advanced WAF and BIG-IP ASM — Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Unknown · BIG-IP Advanced WAF and BIG-IP ASM
9.8CriticalCVSS 3.1
Within 72 hours
Patch availableCritical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityCritical→Operational priority:Critical, unchanged from published severity.unchanged
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs Unknown BIG-IP Advanced WAF and BIG-IP ASM and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded.
Patch available01
What, why and how
On BIG-IP versions 16.0.x before 16.0.1.1, 15.1.x before 15.1.2.1, 14.1.x before 14.1.4, 13.1.x before 13.1.3.6, 12.1.x before 12.1.5.3, and 11.6.x before 11.6.5.3, a malicious HTTP response to an Advanced WAF/BIG-IP ASM virtual server with Login Page configured in its policy may trigger a buffer overflow, resulting in a DoS attack. In certain situations, it may allow remote code execution (RCE), leading to complete system compromise. Note: Software versions which have reached End of Software Development (EoSD) are not evaluated.
What
On BIG-IP versions 16.0.x before 16.0.1.1, 15.1.x before 15.1.2.1, 14.1.x before 14.1.4, 13.1.x before 13.1.3.6, 12.1.x before 12.1.5.3, and 11.6.x before 11.6.5.3, a malicious HTTP response to an Advanced WAF/BIG-IP ASM virtual server with Login Page configured in its policy may trigger a buffer overflow, resulting in a DoS attack. In certain situations, it may allow remote code execution (RCE), leading to complete system compromise. Note: Software versions which have reached End of Software Development (EoSD) are not evaluated.
Why
The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.
What
On BIG-IP versions 16.0.x before 16.0.1.1, 15.1.x before 15.1.2.1, 14.1.x before 14.1.4, 13.1.x before 13.1.3.6, 12.1.x before 12.1.5.3, and 11.6.x before 11.6.5.3, a malicious HTTP response to an Advanced WAF/BIG-IP ASM virtual server with Login Page configured in its policy may trigger a buffer overflow, resulting in a DoS attack. In certain situations, it may allow remote code execution (RCE), leading to complete system compromise. Note: Software versions which have reached End of Software Development (EoSD) are not evaluated.
Why
The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') → execute code or commands in the affected security context
- Attack surface
- Network
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- None
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-120 ↗
CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow'). The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.- Post-exploitation / living off the land
- After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Patch available
- Action
- Apply the fixed release for the affected product branch as recorded by Canadian Centre for Cyber Security. Validate the exact product and build in the linked advisory before deployment.
- Workaround
- No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04
Evidence and provenance
Published 31 Mar 2021 · Last source change 3 Aug 2024, 18:58 UTC · CWE-120 · Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2021-10110
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceNIST NVD
NVD statusNVD modified after enrichment
Missing structured fields: affected product. Missing data is not evidence of low risk; review the primary advisory.
Material change intelligence
View recent updates ↗What changed after publication
- Affected versionsThe structured affected or fixed version information changed.Canadian Centre for Cyber Security ↗
- Before
- 16.0.x before 16.0.1.1, 15.1.x before 15.1.2.1, 14.1.x before 14.1.4, 13.1.x before 13.1.3.6, 12.1.x before 12.1.5.3, 11.6.x before 11.6.5.3 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
- After
- 16.0.x before 16.0.1.1, 15.1.x before 15.1.2.1, 14.1.x before 14.1.4, 13.1.x before 13.1.3.6, 12.1.x before 12.1.5.3, 11.6.x before 11.6.5.3 · Fixed: The Cyber Centre recommends organizations review all impacted F5 appliances and virtual deployments and patch to one of the below recommended versions. [ 1 ] BIG-IP: Versions 16.0.0 to 16.0.1 should be upgraded to 16.0.1.1 Versions 15.1.0 to 15.1.2 should be upgraded to 15.1.2.1 Versions 14.1.0 to 14.1.3.1 should be upgraded to 14.1.4 Versions 13.1.0 to 13.1.3.5 should be upgraded to 13.1.3.6 Versions 12.1.0 to 12.1.5.2 should be upgraded to 12.1.5.3 Versions 11.6.1 to 11.6.5.2 should be upgraded to 11.6.5.3 BIG-IQ: Version 8.0.0 is unaffected Versions 7.1.0 to 7.1.0.2 should be upgraded to 8.0.0 Versions 7.0.0 to 7.0.0.1 should be upgraded to 7.1.0.3 Versions 6.0.0 to 6.1.0 should be upgraded to 7.0.0.2 F5 indicates that if a fixed version has not been identified for a branch used by an organization then no update is available. F5 recommends that organizations upgrade to a version with an available patch. Organizations may use the F5 platform matrix to determine compatible software versions for their F5 platform. [ 1 ] While the Cyber Centre strongly encourages patching as soon as possible, administrators should consider applying the mitigations described in the F5 KB articles if patching is not immediately possible. See the [ 4 ] and [ 5 ] for more details. In summary: Block iControl REST access through the self IP address. Block iControl REST access through the management interface. Block Configuration utility access through self IP addresses. Block Configuration utility access through the management interface. Patching as described in this section also fixes the buffer overflow vulnerabilities described in the previous section. There are no mitigations against CVE-2021-22991 other than patching, while for CVE-2021-22992 F5 has provided an iRule mitigation. [ 9 ] In all cases, the Cyber Centre and F5 recommend patching as the primary mitigation.
- Remediation statusRemediation status changed from Awaiting fix to Patch available.Canadian Centre for Cyber Security ↗
- Before
- Awaiting fix
- After
- Patch available
CVE published
Fixed release recorded from official guidance
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.