CVE-2026-4965Public exploitNetwork attack vector

Unauthenticated code execution via unsafe type annotation evaluation

Published Mar 27, 2026 · Updated Mar 27, 2026

Code injection in Letta 0.16.4 allows remote attackers to execute operating-system commands through crafted tool annotations. The resolve_type function falls back to eval with Python built-ins when process_tool_arguments enables unsafe evaluation, causing an annotation expression to execute during argument coercion. A reachable self-hosted API that accepts and runs attacker-defined tools is required; successful exploitation compromises the server process.

CVSS severity9.8
Critical
EPSS probability0.60%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in Letta 0.16.4 allows remote attackers to execute operating-system commands through crafted tool annotations. The resolve_type function falls back to eval with Python built-ins when process_tool_arguments enables unsafe evaluation, causing an annotation expression to execute during argument coercion. A reachable self-hosted API that accepts and runs attacker-defined tools is required; successful exploitation compromises the server process.

The record

CVE
CVE-2026-4965
Published
Mar 27, 2026
Updated
Mar 27, 2026
Vendor
Letta
Product
Letta
Classifications
CWE-95, CWE-94, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.16.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Letta · Lettaversion=0.16.4

Published CVSS scores

7.5VulDBAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
5.5VulDBCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P
7.3VulDBCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-95Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection')
CWE-94Improper Control of Generation of Code ('Code Injection')
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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