# CVE-2026-89028: MikroTik RouterOS heap corruption in SMB1 SessionSetupAndX

Source: https://junglewise.ai/threats/cve-2026-89028-mikrotik-routeros-heap-corruption-in-smb1-sessionsetupandx  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-16. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-89028 · Severity: high · CVSS 7.5 · Published 2026-09-16

MikroTik RouterOS includes a file sharing daemon (SMB) that allows network-attached devices to share files and printers. A flaw in the SMB1 protocol handler permits remote attackers to send a malformed file-sharing request that triggers a memory corruption vulnerability, potentially crashing the router or allowing arbitrary code execution. This affects routers running RouterOS versions before 7.24.

Technologies: [MikroTik RouterOS](https://junglewise.ai/threats/technologies/routeros). Vendors: [MikroTik](https://junglewise.ai/threats/vendors/mikrotik).

## Quick answers

**Is CVE-2026-89028 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-89028 being exploited in the wild.

**How severe is CVE-2026-89028?** High severity, with a CVSS score of 7.5, published 16 September 2026.

**Which products and versions are affected?** MikroTik RouterOS before 7.24 (including 6.49.18 and earlier, 7.0.0 through 7.11.2).

**Is there a fix for CVE-2026-89028?** A patch was published on 2026-08-14: RouterOS 7.24 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-89028 attacked?** It is attacked over the network, in device firmware.

**Am I affected by CVE-2026-89028?** Check whether you run MikroTik RouterOS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a heap-based buffer overflow caused by integer underflow in the SMB1 SessionSetupAndX handler. When processing a crafted SMB1 request with a malicious uniPwdLen field value, the daemon fails to properly validate the value, leading to integer wraparound. This underflowed value is then used as the length parameter in a memory copy operation, causing data to be written beyond the bounds of an allocated heap buffer. The attack is network-reachable and requires no authentication or user interaction. An attacker can corrupt adjacent heap memory, potentially achieving denial of service or code execution. The vulnerability was fixed in RouterOS version 7.24 released in August 2026.

## Affected products

- MikroTik RouterOS before 7.24 (including 6.49.18 and earlier, 7.0.0 through 7.11.2)

## Timeline

- 2026-09-16: disclosed
- 2026-08-14: patched: RouterOS 7.24 released

## References

- [https://forum.mikrotik.com/t/7-24-stable-is-released/272381](https://forum.mikrotik.com/t/7-24-stable-is-released/272381)
- [https://www.vulncheck.com/advisories/mikrotik-routeros-heap-corruption-via-smb1-sessionsetupandx](https://www.vulncheck.com/advisories/mikrotik-routeros-heap-corruption-via-smb1-sessionsetupandx)

## Related threats

- [MikroTik RouterOS session token replay authentication bypass in WebFig](https://junglewise.ai/threats/cve-2026-89035-mikrotik-routeros-through-7-24-5-contains-a-session-token-replay)
- [MikroTik RouterOS integer overflow in ipt_SAME module](https://junglewise.ai/threats/cve-2026-112158-a-weakness-has-been-identified-in-mikrotik-routeros-up-to-6-40-5)
- [MikroTik RouterOS WinBox incorrect authorization in authentication](https://junglewise.ai/threats/cve-2026-103903-an-incorrect-authorization-vulnerability-in-the-winbox)
- [MikroTik RouterOS integer underflow](https://junglewise.ai/threats/cve-2026-84411-mikrotik-routeros)
- [MikroTik RouterOS improper input validation in BGP labelled-VPN NLRI](https://junglewise.ai/threats/cve-2026-93345-mikrotik-routeros-before-7-25beta4-contains-an-improper-input)