Quadratic Behavior in xml.etree.ElementPath Index Predicates
`Element.findall()` and fully-consumed `Element.iterfind()` exhibit `O(n^2)` time complexity when using XPath index predicates (e.g. `[1]`, `[last()]`, `[last()-N]`) on XML documents with many same-tag siblings. `Element.find()` is only affected when the first match is near the end of the sibling list, such as with `[last()]` or `[last()-N]`; `.//item[1]` short-circuits after the first match.
- Published
- Jul 28, 2026
- Updated
- Aug 13, 2026
- EPSS
- 0.6% · 46th percentile
- CWE
- CWE-407
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Report tools
Action score
8
Monitor
Low priority for now.
- CVSS
- 8 / 40 · 2.0 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.6%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · PSF
- 2.0
- NVD has not scored this yet; the score shown is the CNA’s.
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (PSF). Independent of NVD's CPE analysis and usually ahead of it.
Python Software Foundation CPython
- before 3.10.21affected · python
- 3.11.0 and later · before 3.11.16affected · python
- 3.12.0 and later · before 3.12.14affected · python
- 3.13.0 and later · before 3.13.15affected · python
- 3.14.0 and later · before 3.14.7affected · python
- 3.15.0a1 and later · before 3.15.0rc1affected · python
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Alpine:v3.24 | python3 | before 3.14.7-r0 | 3.14.7-r0 |
| Debian:12 | pypy3 | all versions | — |
| Debian:12 | python3.11 | all versions | — |
| Debian:13 | python3.13 | before 3.13.5-2+deb13u5 | 3.13.5-2+deb13u5 |
| Debian:14 | pypy3 | before 8.0.0+dfsg-1 | 8.0.0+dfsg-1 |
| Debian:14 | python3.13 | before 3.13.15-1 | 3.13.15-1 |
| Debian:14 | python3.14 | before 3.14.7-1 | 3.14.7-1 |
| openSUSE:Tumbleweed | python313 | before 3.13.15-1.1 | 3.13.15-1.1 |
| openSUSE:Tumbleweed | python315 | before 3.15.0~rc2-1.1 | 3.15.0~rc2-1.1 |
| Red Hat:hummingbird:1 | python-unversioned-command | before 0:3.14.6-2.2.hum1 | 0:3.14.6-2.2.hum1 |
| Red Hat:hummingbird:1 | python-unversioned-command | before 0:3.14.7-1.hum1 | 0:3.14.7-1.hum1 |
| Red Hat:hummingbird:1 | python3 | before 0:3.14.6-2.2.hum1 | 0:3.14.6-2.2.hum1 |
| Red Hat:hummingbird:1 | python3 | before 0:3.14.7-1.hum1 | 0:3.14.7-1.hum1 |
| Red Hat:hummingbird:1 | python3.10 | before 0:3.10.20-3.2.hum1 | 0:3.10.20-3.2.hum1 |
| Red Hat:hummingbird:1 | python3.11 | before 0:3.11.15-5.5.hum1 | 0:3.11.15-5.5.hum1 |
| Red Hat:hummingbird:1 | python3.12 | before 0:3.12.13-3.8.hum1 | 0:3.12.13-3.8.hum1 |
| Red Hat:hummingbird:1 | python3.13 | before 0:3.13.14-1.7.hum1 | 0:3.13.14-1.7.hum1 |
| Red Hat:hummingbird:1 | python3.13 | before 0:3.13.15-1.hum1 | 0:3.13.15-1.hum1 |
| Red Hat:hummingbird:1 | python3.14 | before 0:3.14.7-1.hum1 | 0:3.14.7-1.hum1 |
| Red Hat:hummingbird:1 | python3.14 | before 0:3.14.6-2.2.hum1 | 0:3.14.6-2.2.hum1 |
Same product
python software foundation: all recordsOther highest-scoring records for the same primary product.
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- CVE-2026-6100Use-after-free in lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile after re-use under memory pressure36Monitor
- CVE-2026-3298Out-of-bounds write in Windows asyncio.ProacterEventLoop.sock_recvfrom_into() when using nbytes35Monitor
- CVE-2024-12254Unbounded memory buffering in SelectorSocketTransport.writelines()35Monitor
- CVE-2024-8088Infinite loop when iterating over zip archive entry names from zipfile.Path34Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Python Software Foundation CPython | 3.10.21 | Vendor (CNA) |
| Python Software Foundation CPython | 3.11.16 | Vendor (CNA) |
| Python Software Foundation CPython | 3.12.14 | Vendor (CNA) |
| Python Software Foundation CPython | 3.13.15 | Vendor (CNA) |
| Python Software Foundation CPython | 3.14.7 | Vendor (CNA) |
| Python Software Foundation CPython | 3.15.0rc1 | Vendor (CNA) |
| azl3 python3 3.12.9-13 on Azure Linux 3.0 | 3.12.9-14 · CBL-Mariner Releases | Microsoft (MSRC) |
| azl3 python3 3.12.9-14 on Azure Linux 3.0 | 3.12.9-14 · CBL-Mariner Releases | Microsoft (MSRC) |
| alpine:python3 | 3.14.7-r0 · Alpine:v3.24 | Package registry (OSV) |
| debian:pypy3 | 8.0.0+dfsg-1 · Debian:14 | Package registry (OSV) |
| debian:python3.13 | 3.13.5-2+deb13u5 · Debian:13 | Package registry (OSV) |
| debian:python3.14 | 3.14.7-1 · Debian:14 | Package registry (OSV) |
| opensuse:python313 | 3.13.15-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| opensuse:python315 | 3.15.0~rc2-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| red hat:python-unversioned-command | 0:3.14.6-2.2.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:python3 | 0:3.14.6-2.2.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:python3.10 | 0:3.10.20-3.2.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:python3.11 | 0:3.11.15-5.5.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:python3.12 | 0:3.12.13-3.8.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:python3.13 | 0:3.13.14-1.7.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:python3.14 | 0:3.14.6-2.2.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- Petr Viktorin (https://github.com/encukou)coordinator
- dm (https://github.com/DarkaMaul)reporter
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-327655 days apartPotential DoS via quadratic complexity in unicodedata.normalize()25Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- Administrator privileges are required.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- Integrity
- Availability
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- High
- User interaction
- P
- Scope
- X
Weakness class (CWE)
CWE-407 · Inefficient Algorithmic ComplexityCVSS vector
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:P/VC:N/VI:N/VA:L/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
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- github.com/python/cpython/commit/02c08e6b747ac43d0d866a4ffa916bedf3423f81
- github.com/python/cpython/commit/037965c00a427cba5c05447efadc67c51a492e85
- github.com/python/cpython/commit/0583f24ae678993e3f7939f51ad5bcae5ad9dc70
- github.com/python/cpython/commit/2ffab083782968a4d732738f4f1dff6bbd69d2b0
- github.com/python/cpython/commit/390337b8ba1658833fdef379e1739c9f9533a8db
- github.com/python/cpython/commit/96510a3758f4a075f43223afdee3b6ee1a7a7f02
- github.com/python/cpython/commit/cb409342a19f25656f62e679f8bac265fe1442c3
- github.com/python/cpython/issues/152674
- github.com/python/cpython/pull/152676
- mail.python.org/archives/list/security-announce@python.org/thread/7YMZ6DDZVR26TJJBVO3RDNBAVGHNYAKR/
Vendor advisories and official records. Exploit/PoC links are deliberately left out.