How severe is CVE-2026-34515?

No CVSS score has been assigned to CVE-2026-34515 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-34515?

CVE-2026-34515 affects the following packages: aiohttp (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-34515?

Update aiohttp to 3.13.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34515 is resolved across your whole dependency graph.

How do I detect CVE-2026-34515 in my PyPI dependencies?

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

How do I mitigate CVE-2026-34515 if there is no patch (or I can't update yet)?

Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Is CVE-2026-34515 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-34515 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-2026-34515?

CVE-2026-34515 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 39th 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-2026-34515?

CVE-2026-34515 is classified as CWE-36 (CWE-36), Server-Side Request Forgery (SSRF) (CWE-918). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-34515 published, and has it been updated?

CVE-2026-34515 was published on April 1, 2026 and was last updated on October 28, 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-2026-34515 — aiohttp

Fix: aio-libs/aiohttp@0ae2aa0

CVE-2026-34515 is a CWE-36 vulnerability in aiohttp. A fix is available for aiohttp — see the affected versions and patch details below.

AIOHTTP: UNC SSRF/NTLMv2 Credential Theft/Local File Read in static resource handler on Windows

Also known asGHSA-p998-jp59-783mPYSEC-2026-2097

Published

Apr 1, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34515.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs39th percentile — riskier than 39% of all scored CVEsHighest risk

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

Real-World Exposure

1 pkg affected

🐍aiohttp

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

Summary

On Windows the static resource handler may expose information about a NTLMv2 remote path.

Impact

If an application is running on Windows, and using aiohttp's static resource handler (not recommended in production), then it may be possible for an attacker to extract the hash from an NTLMv2 path and then extract the user's credentials from there.

Patch: https://github.com/aio-libs/aiohttp/commit/0ae2aa076c84573df83fc1fdc39eec0f5862fe3d

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`aiohttp`	all versions	3.13.4`pip install --upgrade 'aiohttp==3.13.4'`

Affected Products

1 product · 1 configurations

Application

aiohttpaiohttp

< 3.13.4

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aiohttp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update aiohttp to 3.13.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34515 is resolved across your whole dependency graph.
Workarounds
Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Source: Red Hat security advisory for CVE-2026-34515 (CC BY 4.0)

Frequently Asked Questions

### Summary On Windows the static resource handler may expose information about a NTLMv2 remote path. ### Impact If an application is running on Windows, and using aiohttp's static resource handler (not recommended in production), then it may be possible for an attacker to extract the hash from an NTLMv2 path and then extract the user's credentials from there. ----- Patch: https://github.com/aio-libs/aiohttp/commit/0ae2aa076c84573df83fc1fdc39eec0f5862fe3d

O3 Security · Impact-Aware SCA

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