Description
UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| ultrajson | ultrajson | < 5.12.1 | — |
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 | ujson | 5.13.0-1 | — |
| Debian 13 | ujson | No fix yet | — |
| Debian 12 | ujson | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | ujson +1 | No fix yet | — |
| Ubuntu 26.04 LTS | ujson | No fix yet | — |
| Ubuntu 25.10 | ujson +1 | No fix yet | — |
| Ubuntu 20.04 LTS | pandas | No fix yet | — |
| Ubuntu 18.04 LTS | pandas +1 | No fix yet | — |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 16.04 LTS | pandas +1 | No fix yet | — |
| Ubuntu 14.04 LTS | pandas | No fix yet | — |
| Ubuntu Pro 24.04 LTS | ujson | No fix yet | — |
| Ubuntu Pro 22.04 LTS | ujson | No fix yet | — |
| Ubuntu Pro 20.04 LTS | ujson | No fix yet | — |
| Ubuntu Pro 18.04 LTS | ujson | No fix yet | — |
| Ubuntu Pro 16.04 LTS | ujson | No fix yet | — |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | python-ujson | 1.35-150100.3.13.1 | SUSE-SU-2026:3539-1 |
| SLES 15 SP6 | python-ujson | 1.35-150100.3.13.1 | SUSE-SU-2026:3539-1 |
| SLES 15 SP5 | python-ujson | 1.35-150100.3.13.1 | SUSE-SU-2026:3539-1 |
| SLES 15 SP4 | python-ujson | 1.35-150100.3.13.1 | SUSE-SU-2026:3539-1 |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | python-ujson | 5.10.0-160000.3.1 | SUSE-SU-2026:23136-1, SUSE-SU-2026:23114-1 |
| SLES for SAP 15 SP6 | python-ujson | 1.35-150100.3.13.1 | SUSE-SU-2026:3539-1 |
| SLES for SAP 15 SP5 | python-ujson | 1.35-150100.3.13.1 | SUSE-SU-2026:3539-1 |
| SLES for SAP 15 SP4 | python-ujson | 1.35-150100.3.13.1 | SUSE-SU-2026:3539-1 |
| SLES 16.0 | python-ujson | 5.10.0-160000.3.1 | SUSE-SU-2026:23136-1, SUSE-SU-2026:23114-1 |
| SLE HPC 15 SP5 | python-ujson | 1.35-150100.3.13.1 | SUSE-SU-2026:3539-1 |
| SLE HPC 15 SP4 | python-ujson | 1.35-150100.3.13.1 | SUSE-SU-2026:3539-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | python-ujson | 5.10.0-160000.3.1 | openSUSE-SU-2026:21518-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| PyPI | ujson | < 5.12.1 | 5.12.1 | GHSA-c38f-wx89-p2xg |
Advisories 4
- SUSE-SU-2026:23136-1 Security update for python-ujson SUSE / openSUSE Security Updates · Aug 14, 2026
- SUSE-SU-2026:23114-1 Security update for python-ujson SUSE / openSUSE Security Updates · Aug 14, 2026
- SUSE-SU-2026:3539-1 Security update for python-ujson SUSE / openSUSE Security Updates · Aug 11, 2026
- openSUSE-SU-2026:21518-1 Security update for python-ujson SUSE / openSUSE Security Updates · Aug 5, 2026