Description
libexpat through 2.10.0 contains an out-of-bounds read vulnerability in unknown_toUtf8() and unknown_toUtf16() in xmltok.c when handling application-registered unknown encodings. Attackers can supply a document ending in a truncated multibyte sequence so the convert callback reads past the parse buffer, leaking adjacent memory or crashing applications.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| libexpat | libexpat | ≤ 2.10.0 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | expat | No fix yet | — |
| Debian 13 | expat | No fix yet | — |
| Debian 12 | expat | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | tdom +6 | No fix yet | — |
| Ubuntu 26.04 LTS | tdom +5 | No fix yet | — |
| Ubuntu 24.04 LTS | tdom +4 | No fix yet | — |
| Ubuntu 22.04 LTS | tdom +5 | No fix yet | — |
| Ubuntu 20.04 LTS | tdom +4 | No fix yet | — |
Show 9 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | gdcm +7 | No fix yet | — |
| Ubuntu 16.04 LTS | gdcm +6 | No fix yet | — |
| Ubuntu Pro 26.04 LTS | swish-e | No fix yet | — |
| Ubuntu Pro 24.04 LTS | swish-e +2 | No fix yet | — |
| Ubuntu Pro 22.04 LTS | swish-e +2 | No fix yet | — |
| Ubuntu Pro 20.04 LTS | expat +3 | No fix yet | — |
| Ubuntu Pro 18.04 LTS | coin3 +4 | No fix yet | — |
| Ubuntu Pro 16.04 LTS | vtk +8 | No fix yet | — |
| Ubuntu Pro 14.04 LTS | vtk +4 | No fix yet | — |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | cmake +2 | No fix yet | — |
Wolfi
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Wolfi rolling | expat +3 | No fix yet | — |
Advisories 1
- WID-SEC-2026-4387 expat: Schwachstelle ermöglicht Denial of Service BSI CERT-Bund (WID) · Nov 10, 2026
References
- https://github.com/libexpat/libexpat/pull/1492 patch issue-tracking
- https://github.com/libexpat/libexpat/blob/a70841d9ffa64ddde29ab824ed6305035ebe4c47/expat/lib/xmltok.c#L1274-L1322 technical-description
- https://github.com/libexpat/libexpat product
- VulnCheck Advisory: libexpat through 2.10.0 Out-of-Bounds Read via unknown_toUtf8 and unknown_toUtf16 third-party-advisory