What is CVE-2026-3989?

CVE-2026-3989 is a high-severity vulnerability in Lmsys Sglang, classified under Deserialization of Untrusted Data. CVSS score: 7.8/10. Published 2026-03-12.

How severe is CVE-2026-3989?

High severity. CVSS v3 base score is 7.8 out of 10.

Deserialization in Lmsys Sglang

CVE-2026-3989

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.

Vulnerability class: Insecure Deserialization

EPSS: 0.003 (25.4th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

Affected products

Lmsys Sglang
Sglang — versions 0.5.10

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

References

cret@cert.org (Product)
cret@cert.org (Exploit, Third Party Advisory)
cret@cert.org (Release Notes)
cret@cert.org (Patch, Issue Tracking)

Frequently asked questions

What is CVE-2026-3989?: CVE-2026-3989 is a high-severity vulnerability in Lmsys Sglang, classified under Deserialization of Untrusted Data. CVSS score: 7.8/10. Published 2026-03-12.
How severe is CVE-2026-3989?: High severity. CVSS v3 base score is 7.8 out of 10.