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🛡️ CVE-2026-56403 on Debian 11 (Root.io) — expat

🟡 CVSS 5.0 — Medium ✅ No Known Exploit OSV
5.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

CVE-2026-56403 in expat - Patched by Root

Root has patched CVE-2026-56403 in the expat package for Root:Debian:11. Multiple fixed versions available.

Distribution advisory

This page covers CVE-2026-56403 as tracked by Debian 11 (Root.io), for the package expat. The fix is available in version 2.2.10-2+deb11u7.root.io.16; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability low. (rating taken from the base CVE record.)

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

  • Attack vector: Local — a local account, shell or session on the host is needed.
  • Attack complexity: High — the attacker first has to win a race, learn a secret or otherwise prepare the target.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: Low — limited, and the attacker does not choose what is affected.

Weakness class

ROOT-OS-DEBIAN-11-CVE-2026-56403 is classified as CWE-190: Integer Overflow or Wraparound. Arithmetic produces a value too large for its type and wraps around, so a later size or bounds check passes when it should not.

Affected software

ROOT-OS-DEBIAN-11-CVE-2026-56403 is recorded against 2 packages.

  • expat (fixed in 2.2.10-2+deb11u7.root.io.16)
  • rootio-expat (fixed in 2.2.10-2+deb11u7.root.io.16)

Timeline and source

Published on 20 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

Other advisories for this package

expat has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-190: Integer Overflow or Wraparound) in other software:

Details

Severity MEDIUM
CVSS Score 5.0
CVSS Vector N/A
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-08-20
Updated 2026-08-20
Modified 2026-08-20
Fix URL N/A

Affected Packages

Software From version Fixed in
expat — 2.2.10-2+deb11u7.root.io.16
rootio-expat — 2.2.10-2+deb11u7.root.io.16

References

N/A

Vulnerability Monitoring

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