NLTK versions before 3.10.3 use xml.etree.ElementTree to parse XML in multiple modules, which honors entity declarations in document DTDs. Attackers can craft XML payloads with nested entity declarations that expand from hundreds of bytes to megabytes in memory, causing denial of service.
CVE-2026-78681
HIGHPre-NVD 7.57.5—Trending — 4 sources updated this week
EchelonGraph scoreHIGH confidence
Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-08-25. a secondary CVSS source baseline 7.5; sources differ by 0.0.
Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.5Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.5
- EG Score
- 7.5(high)
- EG Risk
- 38(Track)EG Risk 38/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity75% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 20%
- KEV
- Not listed
Published
August 25, 2026
Last Modified
August 25, 2026
Advisory Details (2)
Auto-updated Aug 25, 2026🔬 Proof of concept available. Patch available. Sources: github.
generic
NLTK before 3.10.3 Entity Expansion DoS via ElementTree | Advisories | VulnCheck
https://www.vulncheck.com/advisories/nltk-before-entity-expansion-dos-via-elementtreegithub Patch Available🟡 PoC Available
Entity-expansion DoS (billion laughs) via remaining raw ElementTree parses (CWE-776) · Advisory · nltk/nltk · GitHub
https://github.com/nltk/nltk/security/advisories/GHSA-97qj-x29f-37w7Vendor Advisories for CVE-2026-78681(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 7× in last 7d / 7× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-08-26 02:46 UTCGHSA enrichment
- 2026-08-25 14:32 UTCEG score recompute
- 2026-08-25 14:32 UTCGHSA enrichment
- 2026-08-25 13:49 UTCEPSS rescore
- 2026-08-25 02:19 UTCEG score recompute
- 2026-08-25 01:50 UTCEG score recompute
- 2026-08-25 01:50 UTCMITRE cvelistV5first tracked
Frequently asked(5)
What is CVE-2026-78681?
CVE-2026-78681 is a high vulnerability published on August 25, 2026. NLTK versions before 3.10.3 use xml.etree.ElementTree to parse XML in multiple modules, which honors entity declarations in document DTDs. Attackers can craft XML payloads with nested entity declarations that expand from hundreds of bytes to megabytes in memory, causing denial of service.
When was CVE-2026-78681 disclosed?
CVE-2026-78681 was first published in the National Vulnerability Database on August 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-78681 actively exploited?
CVE-2026-78681 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 80.2% of all scored CVEs.
What is the CVSS score of CVE-2026-78681?
CVE-2026-78681 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-78681?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-78681, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-78681
Is Your Infrastructure Affected by CVE-2026-78681?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.