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smb: some SMB flows can cause resource exhaustion

Moderate
jasonish published GHSA-hvvj-c8xx-9g35 Jul 21, 2026

Software

Suricata

Affected versions

>= 8.0.0, < 8.0.6
< 7.0.17

Patched versions

8.0.6
7.0.17

Description

Impact

Suricata's SMB parser could retain force-completed transactions on flows where Suricata observed only one direction with payload. When the SMB transaction cap was reached, older transactions were marked parser-complete but not skipped for inspection in the missing direction, so cleanup would not reclaim them. A sustained one-directional SMB flow could therefore grow per-flow transaction state without bound and make cleanup re-scan an increasing transaction list, leading to CPU and memory exhaustion.

Patches

Upgrade to Suricata 8.0.6 or 7.0.17.

Workarounds

You can use a rule like alert smb any any -> any any (msg:"SURICATA SMB too many transactions"; app-layer-event:smb.too_many_transactions; bypass; classtype:protocol-command-decode; sid:1;)

References

https://redmine.openinfosecfoundation.org/issues/8629

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

CVE ID

CVE-2026-63448

Weaknesses

Uncontrolled Resource Consumption

The product does not properly control the allocation and maintenance of a limited resource. Learn more on MITRE.

Missing Release of Memory after Effective Lifetime

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse. Learn more on MITRE.

Inefficient Algorithmic Complexity

An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached. Learn more on MITRE.