Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:L) | Local access needed |
| Attack complexity (AC:L) | Low complexity |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:N) | No user interaction |
| Scope (S:U) | Scope unchanged |
| Confidentiality (C:H) | High confidentiality impact |
| Integrity (I:H) | High integrity impact |
| Availability (A:L) | Low availability impact |
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
About Xmlsoft Libxml2
CVE-2026-86140 affects Xmlsoft Libxml2, a product from Xmlsoft. Before acting, confirm where Xmlsoft Libxml2 runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: In libxml2 before 2.15.4, xmlSnprintfElements in valid.c has a strcat stack-based buffer overflow.
The weakness class is Stack Buffer Overflow. A write past the end of a stack buffer can corrupt control data.
Based on its CVSS vector, the flaw needs local or adjacent access, needs no login, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Xmlsoft Libxml2 |
| Affected versions | Libxml2 before 2.15.4 |
| Published | Sep 5, 2026 |
| Last modified | Sep 15, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | cve@mitre.org |
How to detect it
- Inventory every instance of Xmlsoft Libxml2 and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Xmlsoft Libxml2 named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Xmlsoft Libxml2 to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-121: Stack Buffer Overflow More CVEs with this weakness
Technical References
Frequently asked questions
Related CVEs
Use After Free in libxml2's xmlParseInternalSubset from GNOME libxml2 version 2.9.11 to 2.11.0 allows a remote attacker to cause a denial-of-service via maliciously crafted XML input with improper entity resolution handling.
Stack buffer overflow vulnerability in D-Link DIR-513 v1.10 via the curTime parameter to goform/formSetDomainFilter.
Stack buffer overflow vulnerability in D-Link DIR-513 v1.10 via the curTime parameter to goform/formSetPortTr.
ALGO 8180 IP Audio Alerter SIP INVITE Alert-Info Stack-based Buffer Overflow Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of ALGO 8180 IP Audio Alerter devices. Authentication is not required to exploit this vulnerability. The specific flaw exists within the handling of the Alert-Info header of SIP INVITE requests. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of the device. Was ZDI-CAN-28301.
In Tenda AC7 v15.03.06.44, the wanSpeed parameter of the route /goform/AdvSetMacMtuWan has a stack buffer overflow vulnerability that can lead to remote arbitrary code execution.
ALGO 8180 IP Audio Alerter SIP INVITE Replaces Stack-based Buffer Overflow Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of ALGO 8180 IP Audio Alerter devices. Authentication is not required to exploit this vulnerability. The specific flaw exists within the handling of the Replaces header of SIP INVITE requests. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of the device. Was ZDI-CAN-28300.
Earn your free CTEM certification.
Learn to scope, prioritize, validate and mobilize fixes for CVEs like CVE-2026-86140 with a free CTEM certification.
Beginner / Practitioner / Program Leader
Explore certifications