CVE-2021-22991

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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, and 12.1.x before 12.1.5.3, undisclosed requests to a virtual server may be incorrectly handled by the Traffic Management Microkernel (TMM) URI normalization, which may trigger a buffer overflow, resulting in a DoS attack. In certain situations, it may theoretically allow bypass of URL based access control or remote code execution (RCE). Note: Software versions which have reached End of Software Development (EoSD) are not evaluated.

CVSS 9.8 (CRITICAL) KEV: KNOWN CATALOG

Attention and evidence

HYPE SCORE

0.0/10

REALITY · THREAT PRIORITY

8.8/10

General review priority; not probability

Evidence confidence: Exploitation recorded

Why this priority?

Recorded exploitation baseline: +7.00
Technical severity: CVSS 9.8: +1.47
Fresh EPSS: 62.42%: +0.31

General review priority, not probability, victim count or asset-specific risk. A range covers missing CVSS/EPSS inputs within the current evidence state.

Sources: 3 documents and public datasets.

Hype components

Headline sample (25%)

0/100

Press, 30 days (60%)

0/100

Grounded branding (15%)

0/100

HYPE TOTAL0/100

Sources and documents

BleepingComputer

Press · 22 Jan 2022, 08:00 · CISA adds 17 vulnerabilities to list of bugs exploited in attacks - BleepingComputer

Rapid7

Press · 18 Mar 2021, 07:00 · F5 Discloses Eight Vulnerabilities—Including Four Critical Ones—in BIG-IP Systems - Rapid7

SOC Prime

Press · 12 Mar 2021, 08:00 · Critical Vulnerabilities in F5 BIG-IP, BIG-IQ Enable Remote Code Execution on Vulnerable Systems - SOC Prime

Score evolution

● Hype ● Reality

Earlier evidence-support scores are retained in history; this chart shows only the current priority definition.

First record: hype 0.0 · reality 8.8 (2026-11-02 15:12). The curve appears once the score changes.

Public exploit evidence

Public exploit entries / repo candidates

Evidence context and dated references

Reality is general threat/review priority, combining observed exploitation, CVSS severity and fresh EPSS. Evidence confidence is separate. This is not calibrated risk, a victim count or an asset-specific assessment. A range reflects missing numeric inputs.

Evidence in context

Confidence in exploitation evidence: Exploitation recorded
Priority basis: Recorded exploitation; CVSS 9.8; EPSS 62.4%
Attention, last 30 days: 0 distinct story titles; 0 press documents; 0 publisher domains.
Technical potential: network access, no prior privileges, no user interaction.
Observed activity: Exploitation recorded in CISA KEV.
Known scale: Not quantified.
Evidence confidence basis: Trusted exploitation confirmation

Score evaluated: 2026-11-05 13:58:23.782764+00:00 · EPSS snapshot: 2026-11-05T12:03:04Z

Source event timeline

First press mention

12 Mar 2021, 08:00

Published

31 Mar 2021, 17:23

Added to the CISA KEV catalog

18 Jan 2022, 00:00

Latest press mention

22 Jan 2022, 08:00

Score calculated

05 Nov 2026, 13:58