VulnerabilityPublished 24 Feb 2026

CVE-2026-25899: gofiber fiber · Excessive Memory Allocation

Affects gofiber fiberSource CVE Database V5

Compare

Not known to be exploited · CVSS 7.5 High : upgrade to 3.1.0 soon.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 39% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.1.0

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 24 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 29 Oct 2026.

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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity 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

Upgrade fiber and github.com/gofiber/fiber to 3.1.0.

Affected software

Product	Affected	Fixed in
gofiberfiber	Affected >=3.0.0 <3.1.0	Fixed in 3.1.0
Gogithub.com/gofiber/fiber`pkg:golang/github.com/gofiber/fiber`Other threats	Affected <3.1.0	Fixed in 3.1.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

To mitigate CVE-2026-25899, organizations should immediately upgrade all GoFiber v3 instances to version 3.1.0 or later, where the vulnerability is fixed. If immediate upgrade is not feasible, implement network-level protections such as Web Application Firewalls (WAFs) or intrusion prevention systems (IPS) to detect and block suspicious requests containing the fiber_flash cookie or unusually sized cookies. Limit the size of incoming cookies at the application or proxy level to prevent oversized allocations. Monitor application logs and server resource usage for unusual memory spikes or crashes indicative of exploitation attempts. Employ rate limiting to reduce the risk of repeated exploitation attempts from a single source. Conduct thorough testing after upgrades to ensure the fix is effective and does not disrupt legitimate traffic. Finally, maintain an inventory of all GoFiber deployments to ensure no vulnerable instances remain in production or staging environments.

Description

Fiber is an Express inspired web framework written in Go. In versions on the v3 branch prior to 3.1.0, the use of the `fiber_flash` cookie can force an unbounded allocation on any server. A crafted 10-character cookie value triggers an attempt to allocate up to 85GB of memory via unvalidated msgpack deserialization. No authentication is required. Every GoFiber v3 endpoint is affected regardless of whether the application uses flash messages. Version 3.1.0 fixes the issue.

Impact

The primary impact of CVE-2026-25899 is denial of service through memory exhaustion. An attacker can remotely cause a GoFiber v3 server to allocate massive amounts of memory, potentially crashing the server or severely degrading its performance. This can disrupt web services and APIs relying on GoFiber, causing downtime and loss of availability. Since no authentication is required, the attack surface is broad, allowing any remote attacker to exploit the vulnerability. Organizations running GoFiber v3-based applications may face service outages, impacting business operations, customer trust, and potentially leading to financial losses. Additionally, in environments where GoFiber is used in microservices or critical infrastructure, the DoS could cascade, affecting dependent systems. Although the vulnerability does not directly impact confidentiality or integrity, the availability impact alone is significant. The lack of known exploits in the wild suggests limited current exploitation, but the vulnerability’s characteristics make it a likely target for attackers once widely known.

CWE-789Memory Allocation with Excessive Size Value (opens in a new tab)
Variant weakness
The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.
Implementation · Architecture and Design
Perform adequate input validation against any value that influences the amount of memory that is allocated. Define an appropriate strategy for handling requests that exceed the limit, and consider supporting a configuration option so that the administrator can extend the amount of memory to be used if necessary.
Operation
Run your program using system-provided resource limits for memory. This might still cause the program to crash or exit, but the impact to the rest of the system will be minimized.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
OWASP ASVS 4.0.3
V8.1.4 (opens in a new tab)
V13.4.1 (opens in a new tab)
V11.1.4 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Mar 2026, 01:51 UTC

WeaknessesCWE-789

Technical details

References

Community reviews

Related threats