🛡️ CVE-2026-56406 — libexpat

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.

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

CVE-2026-56406 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

CVE-2026-56406 is recorded against 1 package.

• libexpat (fixed in 2.8.2)

Timeline and source

Published on 21 June 2026 and last revised on 23 June 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com

Other advisories for this package

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

• CVE-2026-56412 (4.9 Medium, published 21 Jun 2026)
• CVE-2026-56404 (6.9 Medium, published 21 Jun 2026)
• CVE-2026-56411 (6.9 Medium, published 21 Jun 2026)
• CVE-2026-56403 (6.9 Medium, published 21 Jun 2026)
• CVE-2026-56410 (6.9 Medium, published 21 Jun 2026)
• CVE-2026-56409 (6.5 Medium, published 21 Jun 2026)
• CVE-2026-56408 (6.9 Medium, published 21 Jun 2026)
• CVE-2026-56407 (6.9 Medium, published 21 Jun 2026)

Same weakness in other software

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

• CVE-2023-25667 (8.0 High, published 13 Jul 2026)
• CVE-2023-25662 (8.0 High, published 13 Jul 2026)
• CVE-2022-36015 (8.0 High, published 13 Jul 2026)
• CVE-2017-12863 (8.0 High, published 9 Jul 2026)
• CVE-2022-23575 (8.0 High, published 9 Jul 2026)
• CVE-2022-23567 (8.0 High, published 9 Jul 2026)
• CVE-2017-12864 (8.0 High, published 9 Jul 2026)
• CVE-2017-1000450 (8.0 High, published 2 Jul 2026)

Details

Affected Packages

References