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Response snapshot Oct 27, 2026, 02:11 UTC

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VulnerabilityCVE-2026-115775

Twisted: Unauthenticated Remote Denial of Service in the Twisted words domish XML Element Stream via an Unbounded Element Tree

An allocation-without-limits vulnerability in the Twisted XML element stream lets any unauthenticated remote peer exhaust server memory over a single stream.

At a glance

Exploited
Not known
Severity
8.7 High (CVSS 4.0)
Chance of exploitation
0.4% in the next 30 days
Sources
2 independent sources

What to do

GitHub lists first patched versions: Twisted: 26.10.0rc1. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-3476-c5c2-fr73 (opens a new tab)

What happened

## Summary

An allocation-without-limits vulnerability in the Twisted XML element stream lets any unauthenticated remote peer exhaust server memory over a single stream. When the peer opens a container element and streams child elements without ever closing the container, every element is materialised into an in-memory tree with no limit on depth or child count.

An element is released only when its end tag arrives, so a container the attacker never closes retains everything beneath it until the process is killed.

## Details

Continue reading

In `ExpatElementStream._onStartElement`, each start tag appends a new element to the current element's children and descends into it, with no depth or child-count check:

```python # src/twisted/words/xish/domish.py (ExpatElementStream._onStartElement) if self.documentStarted == 1: if self.currElem != None: self.currElem.children.append(e) # append child: no depth/count cap e.parent = self.currElem self.currElem = e # descend into the new element ```

An element is emitted and dropped only when its end tag arrives while it sits directly under the document root, so a container that is never closed keeps every child beneath it. The transport `XmlStream.dataReceived` feeds bytes to `self.stream.parse(data)` with no size limit, and in XMPP the stream is parsed during negotiation before authentication.

Affected product: Twisted, `twisted.words.xish.domish` element stream Affected versions: confirmed against 26.4.0

## PoC

On any endpoint that parses untrusted XML streams with this stack, such as an XMPP server, open a stream by sending the opening `stream:stream` tag and a container element, then stream child elements continuously and never send the container's closing tag. No credentials are required, because in XMPP the stream is parsed before authentication.

Every child is appended to the container and retained because the container is never emitted, and the transport applies no limit on the size of the unfinished document. Because each small element becomes a full object in memory the footprint is many times the traffic sent, so a modest-bandwidth peer, or several such streams, drives the process to memory exhaustion.

## Impact

This is an unauthenticated remote denial of service by memory exhaustion. A single stream grows an in-memory element tree without bound, amplified by per-element object overhead, until the operating system kills the server. There is no confidentiality or integrity impact and no code execution. The affected surface is any deployment that parses untrusted XML streams with this stack, such as an XMPP server or component.

Affected package ranges reported by GitHub: Twisted: <= 26.4.0

Scores and how they were measured

CVSS base severity

8.7

Version 4.0As of

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.4%

Scored Percentile 38.3%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-3476-c5c2-fr73 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-3476-c5c2-fr73, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-3476-c5c2-fr73, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-3476-c5c2-fr73, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  5. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-3476-c5c2-fr73, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  6. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-3476-c5c2-fr73, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  7. Primary source

    NVD CVE-2026-115775 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  8. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  9. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  10. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  11. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  12. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-115775, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 26). Twisted: Unauthenticated Remote Denial of Service in the Twisted words domish XML Element Stream via an Unbounded Element Tree (CVE-2026-115775). https://kevwire.com/record/CVE-2026-115775

MLA

"Twisted: Unauthenticated Remote Denial of Service in the Twisted words domish XML Element Stream via an Unbounded Element Tree (CVE-2026-115775)." KEVWire, 26 Oct. 2026, kevwire.com/record/CVE-2026-115775.

Chicago

KEVWire. "Twisted: Unauthenticated Remote Denial of Service in the Twisted words domish XML Element Stream via an Unbounded Element Tree (CVE-2026-115775)." Last modified October 26, 2026. https://kevwire.com/record/CVE-2026-115775.

Evidence summary (plain text)

Twisted: Unauthenticated Remote Denial of Service in the Twisted words domish XML Element Stream via an Unbounded Element Tree (Oct 23, 2026).
An allocation-without-limits vulnerability in the Twisted XML element stream lets any unauthenticated remote peer exhaust server memory over a single stream. When the peer opens a container element and streams child elements without ever closing the container, every element is materialised into an in-memory tree with no limit on depth or child count. An element is released only when its end tag arrives, so a container the attacker never closes retains everything beneath it until the process is killed.

In `ExpatElementStream._onStartElement`, each start tag appends a new element to the current element's children and descends into it, with no depth or child-count check:
CVSS 8.7 (version 4.0; evidence as of Oct 26, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-115775).
EPSS 0.4% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-115775&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-3476-c5c2-fr73: https://github.com/advisories/GHSA-3476-c5c2-fr73
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo1MTozMFrOAAf0Mg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0OToxMlrOAAf0LQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NzoxN1rOAAf0Kg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NTozNlrOAAf0Jw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
NVD CVE-2026-115775: https://nvd.nist.gov/vuln/detail/CVE-2026-115775
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-26T13:46:51.330Z&lastModEndDate=2026-10-26T15:20:55.429Z&resultsPerPage=500&startIndex=500
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-26T13:11:54.490Z&lastModEndDate=2026-10-26T14:45:57.368Z&resultsPerPage=500&startIndex=500
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-26T12:40:01.998Z&lastModEndDate=2026-10-26T14:10:55.205Z&resultsPerPage=500&startIndex=500
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?pubStartDate=2026-10-12T13:35:55.142Z&pubEndDate=2026-10-26T13:35:55.142Z&resultsPerPage=500&startIndex=9000
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-115775&date=2026-10-26
Record ID: CVE-2026-115775.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 01:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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