PT-2026-39304 · Pypi · Langchain
Dewankpant
+6
·
Published
2026-05-08
·
Updated
2026-06-17
·
CVE-2026-44843
CVSS v3.1
8.2
High
| Vector | AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N |
Name of the Vulnerable Software and Affected Versions
langchain versions prior to 0.3.27
Description
LangChain contains runtime code paths that deserialize inputs, outputs, or other application-controlled payloads using overly broad object allowlists, specifically calling
load() with allowed objects="all". This allows attacker-supplied serialized constructor dictionaries to instantiate trusted classes with untrusted arguments. This issue can lead to Server-Side Request Forgery (SSRF), enabling access to internal services, cloud metadata endpoints, or sensitive network resources, which may result in credential theft and persistent supply-chain compromise.Applications are exposed if they accept untrusted structured input (such as JSON) without validation, preserve attacker-controlled nested dictionaries or lists in run data, and use affected API paths. Known affected surfaces include the
RunnableWithMessageHistory class, the astream log() function, and the astream events(version="v1") function. Additionally, a secret-marker validation bypass in the is lc secret function allows constructor dictionaries to avoid escaping during dumps() to loads() round-trips.Recommendations
Update langchain to version 0.3.27.
Migrate away from the deprecated
RunnableWithMessageHistory class, astream log() function, and astream events(version="v1") function in favor of newer streaming and memory patterns, such as the stream API.
Use load() and loads() only with trusted manifests or objects from trusted storage; do not pass user-controlled data to these functions.
When using load() or loads(), provide a narrow allowed objects value instead of relying on broad defaults or allowed objects="all".Fix
Deserialization of Untrusted Data
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Weakness Enumeration
Related Identifiers
Affected Products
Langchain