How severe is CVE-2026-53870?

No CVSS score has been assigned to CVE-2026-53870 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-53870?

CVE-2026-53870 affects the following packages: hermes-agent (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-53870?

Update hermes-agent to 0.16.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53870 is resolved across your whole dependency graph.

How do I detect CVE-2026-53870 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hermes-agent, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-53870 if there is no patch (or I can't update yet)?

Close the privilege gap rather than the entry point: audit which accounts, roles and service identities can reach the affected operation, drop the component to the least privilege it actually needs, and review file and directory permissions created by earlier installs — a default left in place is what makes this reachable.

Is CVE-2026-53870 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-53870 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-53870?

CVE-2026-53870 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 5th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-53870?

CVE-2026-53870 is classified as Incorrect Default Permissions (CWE-276). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-53870 published, and has it been updated?

CVE-2026-53870 was published on June 17, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-53870 — hermes-agent

Fix: NousResearch/hermes-agent@3bace07

CVE-2026-53870 is a Incorrect Default Permissions vulnerability in hermes-agent. A fix is available for hermes-agent — see the affected versions and patch details below.

Hermes Agent < 0.16.0 - Sensitive File Permission Vulnerability in Store Files

Also known asGHSA-99f9-j8r3-p853PYSEC-2026-2511

Published

Jun 17, 2026

Updated

Oct 21, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 25, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-53870.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk+0.01%

Lower risk than most CVEs5th percentile — riskier than 5% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍hermes-agent

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Hermes Agent before 0.16.0 creates response_store.db and webhook_subscriptions.json with world-readable permissions (mode 0o644), exposing conversation history and HMAC secrets to local users. Attackers with local filesystem access can read these files directly to obtain sensitive data including conversation history, tool payloads, prompts, and per-route HMAC secrets.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`hermes-agent`	all versions	0.16.0`pip install --upgrade 'hermes-agent==0.16.0'`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hermes-agent, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update hermes-agent to 0.16.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53870 is resolved across your whole dependency graph.
Workarounds
Close the privilege gap rather than the entry point: audit which accounts, roles and service identities can reach the affected operation, drop the component to the least privilege it actually needs, and review file and directory permissions created by earlier installs — a default left in place is what makes this reachable.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

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