CVE-2026-11972Public exploitNetwork attack vector

Service interruption via unchecked streaming EOF

Published Jun 23, 2026 · Updated Jun 23, 2026

Denial of service in CPython's tarfile module before 3.10.21 and in affected newer branches allows remote attackers to stall archive parsing. The tarfile._Stream.seek routine trusts an archive member's declared size and continues its block-read loop after read() returns no data at EOF. Reachability requires application code to open an attacker-controlled archive in r| streaming mode; processing then consumes CPU for exponentially increasing time without reading, writing, or corrupting application data.

CVSS severity8.2
High
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in CPython's tarfile module before 3.10.21 and in affected newer branches allows remote attackers to stall archive parsing. The tarfile._Stream.seek routine trusts an archive member's declared size and continues its block-read loop after read() returns no data at EOF. Reachability requires application code to open an attacker-controlled archive in r| streaming mode; processing then consumes CPU for exponentially increasing time without reading, writing, or corrupting application data.

The record

CVE
CVE-2026-11972
Published
Jun 23, 2026
Updated
Jun 23, 2026
Vendor
Python Software Foundation
Product
CPython
Classifications
CWE-252, CWE-770, CWE-606, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 23, 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 <3.16.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Python Software Foundation · CPythonversion=0 <3.16.0

Published CVSS scores

8.2Python Software FoundationCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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-252Unchecked Return Value
CWE-770Allocation of Resources Without Limits or Throttling
CWE-606Unchecked Input for Loop Condition
T1499Endpoint Denial of Service

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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