CVE-2025-27520

published 2025-04-04

CVE-2025-27520: BentoML is a Python library for building online serving systems optimized for AI apps and model inference. A Remote Code Execution (RCE) vulnerability caused…

Priority P1 81 critical 9.8 CVSS 3.1

AV N AC L PR N UI N S U C H I H A H

EXPLOIT

BentoML is a Python library for building online serving systems optimized for AI apps and model inference. A Remote Code Execution (RCE) vulnerability caused by insecure deserialization has been identified in the latest version (v1.4.2) of BentoML. It allows any unauthenticated user to execute arbitrary code on the server. It exists an unsafe code segment in serde.py. This vulnerability is fixed in 1.4.3.

Affected

3 ranges

Vendor	Product	Version range	Fixed in
bentoml	bentoml	—	—
bentoml	bentoml	>= 1.3.4 < 1.4.3	1.4.3
bentoml	bentoml	1.3.4 – 1.4.2	—

Detection & IOCs extracted from sources · hover to see the quote

other application/vnd.bentoml+pickle

path serde.py↗

bytes

|80 04 95|

snort

alert http any any -> $HOME_NET any (msg:"ET WEB_SPECIFIC_APPS BentoML Unauthenticated Remote Command Execution via Insecure Deserialization (CVE-2025-27520)"; flow:established,to_server; http.method; content:"POST"; http.content_type; content:"application/vnd.bentoml+pickle"; fast_pattern; http.request_body; content:"|80 04 95|"; startswith; reference:url,github.com/advisories/GHSA-33xw-247w-6hmc; reference:cve,2025-27520; classtype:web-application-activity; sid:2061788; rev:1; metadata:attack_target Server, tls_state TLSDecrypt, created_at 2025_04_22, cve CVE_2025_27520, deployment Perimeter, deployment Internal, deployment SSLDecrypt, confidence High, signature_severity Major, tag Exploit, updated_at 2025_04_22, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application; target:dest_ip;)

• → Exploit traffic is an HTTP POST request with Content-Type header set to 'application/vnd.bentoml+pickle', indicating a pickle deserialization payload is being submitted to a BentoML endpoint.
• → The request body starts with the byte sequence |80 04 95|, which is the Python pickle protocol 4 opcode header — a reliable startswith anchor for detecting malicious pickle payloads.
• → The vulnerability is unauthenticated; no session token or credential is required, so any inbound POST with the above content-type to a BentoML server should be treated as suspicious. ↗
• → A public Metasploit module exists for this CVE (linux/http/bentoml_rce_cve_2025_27520), indicating active exploitation tooling is available and exploitation attempts should be expected. ↗
• → The root cause is insecure deserialization in serde.py; defenders should audit or monitor file-level access/modifications to this module on BentoML deployments. ↗

• · This vulnerability affects BentoML v1.4.2 specifically and is fixed in v1.4.3. Detection rules targeting this CVE are only relevant for unpatched v1.4.2 deployments. ↗

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