CVE-2025-12084Public exploitNetwork attack vector

Service interruption via quadratic DOM ancestor walks

Published Dec 3, 2025 · Updated Mar 3, 2026

Algorithmic-complexity denial of service in affected CPython releases allows remote attackers to interrupt services via deeply nested DOM trees. Each appendChild() operation triggers _clear_id_cache(), whose _in_document() helper walks the full ancestor chain, making repeated nesting quadratic. Exploitation requires an application to construct attacker-influenced minidom nodes; CPU exhaustion interrupts service without disclosing or modifying data.

CVSS severity6.3
Medium
EPSS probability0.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Algorithmic-complexity denial of service in affected CPython releases allows remote attackers to interrupt services via deeply nested DOM trees. Each appendChild() operation triggers _clear_id_cache(), whose _in_document() helper walks the full ancestor chain, making repeated nesting quadratic. Exploitation requires an application to construct attacker-influenced minidom nodes; CPU exhaustion interrupts service without disclosing or modifying data.

The record

CVE
CVE-2025-12084
Published
Dec 3, 2025
Updated
Mar 3, 2026
Vendor
Python Software Foundation
Product
CPython
Classifications
CWE-407, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 3, 2025CVE publishedPublication date reported by the CVE source.
  2. Mar 3, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=0 <3.10.20
  2. Affected versionversion=3.11.0 <3.11.15
  3. Affected versionversion=3.12.0 <3.12.13
  4. Affected versionversion=3.13.0 <3.13.11
  5. Affected versionversion=3.14.0 <3.14.2
  6. Affected versionversion=3.15.0a1 <3.15.0a3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Python Software Foundation · CPythonversion=0 <3.10.20; version=3.11.0 <3.11.15; version=3.12.0 <3.12.13; version=3.13.0 <3.13.11; version=3.14.0 <3.14.2; version=3.15.0a1 <3.15.0a3

Published CVSS scores

6.3Python Software FoundationCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/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-407Inefficient Algorithmic Complexity
T1499.004Application or System Exploitation

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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