CVE-2026-86142
Description
A flaw in libxml2's xmlXPtrEvalXPtrPart function allows a local attacker to cause a heap-based buffer overflow. An integer overflow while processing an oversized xpointer() expression leads to incorrect memory allocation and an out-of-bounds write, potentially resulting in information disclosure, data corruption, or a denial of service (DoS).
Statement
A heap-based buffer overflow in libxml2's xmlXPtrEvalXPtrPart function enables an out-of-bounds write during the evaluation of oversized xpointer() expressions. The flaw is assigned a Moderate severity rating because exploitation strictly requires local access and complex, multi-gigabyte payload inputs, effectively mitigating the threat of remote or automated system compromise.
Mitigation
To mitigate this applications should avoid passing untrusted XPointer expressions into xmlXPtrEval or XInclude xpointer= attributes and strictly cap input length well below INT_MAX. Additionally, administrators should enforce process or cgroup memory limits to prevent the construction of multi-gigabyte scheme bodies, relying on heap allocator hardening rather than standard fortify flags, which cannot stop this byte-store loop.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.9 | N/A | 6.9 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
cve.org: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Read Memory; Modify Memory; Execute Unauthorized Code or Commands
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. This can often be used to subvert any other security service.
Availability
Technical Impact: Modify Memory; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
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