CVE-2026-3989 in SGLang
Summary
by MITRE • 03/12/2026
SGLangs `replay_request_dump.py` contains an insecure pickle.load() without validation and proper deserialization. An attacker can take advantage of this by providing a malicious .pkl file, which will execute the attackers code on the device running the script.
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Analysis
by VulDB Data Team • 03/17/2026
The vulnerability identified as CVE-2026-3989 resides within the SGLangs replay_request_dump.py script, where insecure deserialization practices create a critical security exposure. This flaw directly violates fundamental security principles by employing pickle.load() without proper validation mechanisms, allowing arbitrary code execution through maliciously crafted pickle files. The vulnerability represents a classic insecure deserialization issue that has been extensively documented in security frameworks and threat models.
The technical implementation of this vulnerability stems from the Python pickle module's inherent dangers when used without proper safeguards. When the replay_request_dump.py script processes user-provided pickle files, it blindly loads the serialized data without verifying its contents or origin. This behavior creates an execution path where attacker-controlled data can be interpreted as executable code, enabling remote code execution on the target system. The flaw aligns with CWE-502, which specifically addresses deserialization of untrusted data, and falls under the ATT&CK technique T1203 for exploitation of remote services through deserialization vulnerabilities.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with complete control over the affected system. An attacker can craft a malicious .pkl file that, when processed by the vulnerable script, executes arbitrary commands with the privileges of the user running the script. This could result in data exfiltration, system compromise, or further lateral movement within a network. The vulnerability is particularly dangerous because it requires minimal user interaction, as the malicious pickle file can be delivered through various attack vectors including email attachments, web downloads, or network transfers.
Mitigation strategies for CVE-2026-3989 must address both immediate remediation and long-term architectural improvements. The primary fix involves replacing pickle.load() with safer serialization alternatives such as JSON or XML, which do not execute arbitrary code during deserialization. Organizations should implement strict input validation and sanitization for all external data sources, ensuring that pickle files are never processed without proper security checks. Additionally, privilege separation should be enforced to limit the impact of potential exploitation, and regular security audits should verify that no other instances of insecure deserialization exist within the codebase. The solution must align with security best practices outlined in industry standards and threat modeling frameworks to prevent similar vulnerabilities from emerging in future development cycles.