VulnerabilityPublished 28 Sep 2026Updated 30 Sep 2026

CVE-2026-84894: Meta Platforms moxygen · Use After Free

Affects Meta Platforms moxygenSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High : upgrade to 004123dd24c30dad6b649163575145f240dabc94 soon.

Data as of 12 Nov 2026, 23:24 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 17% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 004123dd24c30dad6b649163575145f240dabc94

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

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

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: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Sep 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 13 Nov 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.

ghsa-mqcv-532f-gp47

What to do

Upgrade Meta Platforms moxygen to 004123dd24c30dad6b649163575145f240dabc94.

Affected software

Product	Affected	Fixed in
Meta Platforms, Incmoxygen	Affected ≥ b24f8e65cb83ebe5f3880cc4e3a4c8f64e1882f9, < 004123dd24c30dad6b649163575145f240dabc94	Fixed in 004123dd24c30dad6b649163575145f240dabc94

Description

CVE-2026-84894 is a use-after-free vulnerability in Meta Platforms, Inc's moxygen component. The issue occurs before commit 004123dd24c3, where MoQSession::dataStreamReadLoop continues to use a stream read handle after receiving a FIN signal, which invalidates the handle under proxygen's WebTransport API. A remote attacker can trigger this by opening a data stream with an unknown track alias and sending the FIN in the same write. This vulnerability has a high severity with a CVSS score of 7.5 and impacts confidentiality but not integrity or availability.

Impact

The vulnerability allows a remote attacker to cause a use-after-free condition, which can lead to unauthorized disclosure of information (confidentiality impact). There is no indication of impact on integrity or availability. The CVSS score of 7.5 reflects a high severity due to the network attack vector, low attack complexity, and no required privileges or user interaction.

Summary

The vulnerability in moxygen before commit 004123dd24c3 involves MoQSession::dataStreamReadLoop using a stream read handle after it has been invalidated by receiving a FIN signal. This use-after-free condition arises because the handle is kept active despite the FIN, violating proxygen's WebTransport API expectations. An attacker can remotely exploit this by initiating a data stream naming an unknown track alias and including the FIN in the same write operation, causing stale use of the handle.

CWE-416Use After Free (opens in a new tab)
Variant weaknessLikelihood of exploit: HighCWE Top 25 (2025): #7
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
Architecture and Design · Language Selection
Choose a language that provides automatic memory management.
Implementation · Attack Surface Reduction
When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
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

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 5 Oct 2026, 20:32 UTC

WeaknessesCWE-416

Technical details

References

Community reviews

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