CVE-2026-118370
Description
A flaw was found in expat. An integer overflow in the XML attribute parsing logic allows a remote attacker to cause memory corruption and a Denial of Service (DoS). By supplying a specially crafted XML document containing an excessively large number of attributes, an attacker can trigger out-of-bounds memory writes, leading to an application crash.
Statement
This vulnerability is rated Moderate. A signed integer overflow in storeAtts() can lead to process crash; reliable confidentiality/integrity compromise is not demonstrated on Red Hat platforms. Red Hat scores CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H (5.9): Attack Complexity is High because triggering the overflow requires an extreme, multi-gigabyte XML payload with on the order of 2^30 attributes—typically blocked by practical network/memory limits before parse completes. NVD’s higher score (AC:L and I:L) is acknowledged; RH retains AC:H and I:N given payload prerequisites and platform allocator hardening (CME-117), while keeping A:H for crash/DoS.
Mitigation
Reject oversized or attribute-dense untrusted XML before parsing; multi-gigabyte documents with huge attribute counts are required to hit the overflow. Apply process/cgroup memory limits to XML-handling workloads ([CME-114](https://cmetaxonomy.org/entries/CME-114.html), [CME-704](https://cmetaxonomy.org/entries/CME-704.html)). Isolate XML-facing services and restrict to trusted sources ([CME-202](https://cmetaxonomy.org/entries/CME-202.html)). Upgrade to libexpat 2.10.0 or later when available.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.9 | 8.2 | 5.9 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | Low | High |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | None |
| Integrity Impact | None | Low | None |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
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