CVE-2025-55036VulnerabilityPublished 15 Oct 2025Updated 26 Feb 2026

CVE-2025-55036: F5 BIG-IP · Out-of-bounds Write

Affects F5 BIG-IPSource CVE Database V5

Not known to be exploited · CVSS 7.5 High.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 28% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 15 Oct 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
F5 BIG-IP	Affected =17.1.0 =16.1.0 =15.1.0	Fixed in–

AI-suggested

To mitigate CVE-2025-55036, organizations should immediately review their BIG-IP SSL Orchestrator configurations and disable the proxy connect feature on virtual servers where explicit forward proxy is enabled if this feature is not essential. This reduces the attack surface by preventing the vulnerable code path from being triggered. Administrators should monitor F5's security advisories closely and apply vendor-released patches or updates as soon as they become available. In the interim, network-level controls such as filtering or rate limiting suspicious traffic patterns that could trigger the vulnerability may help reduce risk. Conducting thorough testing of BIG-IP configurations and limiting exposure of management and proxy interfaces to trusted networks can further reduce attack vectors. Additionally, organizations should implement comprehensive logging and monitoring to detect anomalous traffic or crashes indicative of exploitation attempts. Regular backups and incident response plans should be updated to prepare for potential service disruptions. Engaging with F5 support for guidance and best practices is recommended to ensure secure deployment.

Description

When BIG-IP SSL Orchestrator explicit forward proxy is configured on a virtual server and the proxy connect feature is enabled, undisclosed traffic may cause memory corruption. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Impact

The primary impact of CVE-2025-55036 is potential denial of service through memory corruption on F5 BIG-IP devices configured with SSL Orchestrator explicit forward proxy and proxy connect enabled. This can disrupt critical network security functions such as SSL inspection, traffic orchestration, and proxying, leading to service outages and degraded security posture. Organizations relying on BIG-IP for perimeter security, encrypted traffic management, or application delivery may experience downtime, impacting business continuity and user access. Although confidentiality and integrity are not directly compromised, the availability impact can indirectly affect security monitoring and incident response capabilities. The vulnerability's remote exploitability without authentication increases the risk of automated attacks or scanning by threat actors. Large enterprises, service providers, and government agencies using BIG-IP appliances in their network infrastructure are particularly vulnerable. The absence of known exploits currently provides a window for proactive mitigation, but the risk of future exploitation remains significant.

CWE-787Out-of-bounds Write (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #5
The product writes data past the end, or before the beginning, of the intended buffer.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Operation · Build and Compilation · Environment Hardening
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index…
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

my.f5.com/manage/s/article/K000151368 (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 27 Feb 2026, 05:36 UTC

WeaknessesCWE-787

Technical details

References

Community reviews

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