CVE-2026-5559 AntaresMugisho PyBlade AST Validation sandbox.py _is_safe_ast special elements used in a template engine
Remote attackers can execute arbitrary code via improper AST validation in the PyBlade template engine, requiring immediate mitigation due to public exploit availability.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-5559?
CVE-2026-5559 is a medium-severity code injection vulnerability in AntaresMugisho PyBlade, published on 5 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
A vulnerability has been found in AntaresMugisho PyBlade 0.1.8-alpha/0.1.9-alpha. The affected element is the function _is_safe_ast of the file sandbox.py of the component AST Validation. Such manipulation leads to improper neutralization of special elements used in a template engine. The attack may be performed from remote. The exploit has been disclosed to the public and may be used. The project was informed of the problem early through an issue report but has not responded yet.
Which versions are affected by CVE-2026-5559?
3 open source packages ship an affected version, including pyblade.
| Package | Affected | Fixed in |
|---|---|---|
pyblade PyPI | From 0.1.8-alpha to 0.2.0-alpha | None |
pyblade PyPI | From 0.1.8-alpha to 0.2.0-alpha | None |
pyblade PyPI | From 0.1.8-alpha to 0.2.0-alpha | None |
How do I fix CVE-2026-5559?
No fix has been published for CVE-2026-5559 yet. Limit exposure of the affected software until one is available.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-5559 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-5559 exists.
Sources
Also known as GHSA-23jg-5f8m-gw8c, PYSEC-2026-2975.