Sapling SCM prior to v0.2.20260929-102736 allows control characters to be embedded in Git subtree URLs. A maliciously constructed repository, when cloned, can cause the program to execute unintended code during read‑only operations such as sl log, blame, or annotate. This flaw arises from insufficient input validation and is classified as CWE‑150.

The vulnerability affects all installations of Meta Platforms, Inc.'s Sapling SCM running a version earlier than v0.2.20260929-102736. Any user or process that can clone a malicious repository through a subtree URL is potentially exposed.

The CVSS score of 7.8 indicates a high severity risk. The EPSS score is not available, so the exploitation probability cannot be quantified, and the vulnerability is not listed in CISA's KEV catalog. The likely attack vector is that an attacker supplies a subtree URL containing control characters in a malicious repository and convinces a target to clone it; upon cloning, the vulnerable code execution path is triggered, allowing the attacker to compromise the target system.