urllib3 is an HTTP client library for Python. From 2.6.2 until 2.8.0, HTTPResponse.stream and HTTPResponse.read_chunked can enter an infinite loop because the Deflate decoder retains trailing bytes as unconsumed input after reaching end-of-stream and repeatedly decodes them without progress. The issue occurs when an untrusted server sends a chunked Deflate response whose decoded body exceeds a positive finite chunk size and whose encoded body has trailing bytes, specifically a response with Transfer-Encoding: chunked and Content-Encoding: deflate, content decoding enabled, and the positive finite amt=N streaming chunk size. The attack mechanism is that a malicious server returns a compressed chunked response with trailing bytes after the Deflate stream. The impact is excessive CPU usage and a request that does not complete, and network read timeouts do not interrupt the loop because no further socket read occurs. This issue is fixed in version 2.8.0.
CVE-2026-97688
This medium-severity CVE scores 6.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (19th percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- Lower severity and no public exploit yet
A fix is available — apply it.
- CVSS v3
- 6.9
- EG Score
- 6.9MEDIUMmedium confidence
- EG Risk
- 46EG Risk 46/100CISA SSVC
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 computedSeverity69% × 45%Exploitation0% × 40%Automatability100% × 15%CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high. - EPSS PROB
- 0.3%
- EPSS %ILE
- 19th
- KEV
- Not listed
CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table
Published
September 29, 2026
Last Modified
September 30, 2026
Advisory Details (3)
Auto-updated Sep 29, 20262.8.0
Patch available: urllib3/urllib3 2.8.0
https://github.com/urllib3/urllib3/releases/tag/2.8.0commit ea2ad7b21a80 (urllib3/urllib3)
Patch available: urllib3/urllib3 2.8.0 (contains commit ea2ad7b21a80)
https://github.com/urllib3/urllib3/commit/ea2ad7b21a80da3632f80016526a18864586077fChunked Deflate streaming can enter an infinite loop · Advisory · urllib3/urllib3 · GitHub
https://github.com/urllib3/urllib3/security/advisories/GHSA-gh4c-6fx4-qh6gVendor Advisories for CVE-2026-97688(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Patch Availability(1)
| Vendor / Ecosystem | Fixed in / Patch | Released | Source |
|---|---|---|---|
| redhat | python-urllib3-main-2.8.0-1.hum1 | 2026-09-21 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(1 across 1 ecosystem)
PyPI(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| urllib3 | 2.6.2, 2.6.3, 2.7.0 | 2.8.0 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
All Vendor Advisories
(1)
Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.
Data Freshness Timeline
(refreshed 18× in last 7d / 18× 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.
- 2026-10-04 11:16 UTCEG score recompute
- 2026-10-04 11:16 UTCVendor advisory
- 2026-10-03 14:26 UTCEPSS rescore
- 2026-10-03 13:24 UTCEG score recompute
- 2026-10-03 13:24 UTCVendor advisory
- 2026-10-02 17:57 UTCEPSS rescore
- 2026-10-02 15:32 UTCEG score recompute
- 2026-10-02 15:32 UTCVendor advisory
- 2026-10-01 19:51 UTCEPSS rescore
- 2026-10-01 17:41 UTCVendor advisory
- 2026-09-30 19:45 UTCEG score recompute
- 2026-09-30 19:45 UTCVendor advisory
- 2026-09-30 15:04 UTCEPSS rescore
- 2026-09-30 14:36 UTCVendor advisory
- 2026-09-29 16:31 UTCEG score recompute
- 2026-09-29 15:53 UTCEG score recompute
- 2026-09-29 15:38 UTCEG score recompute
- 2026-09-29 15:38 UTCMITRE cvelistV5first tracked
Related CVEs(same product + same vendor + same CWE)
Same product
10 shownPyPI:urllib3
Frequently asked(5)
What is CVE-2026-97688?
When was CVE-2026-97688 disclosed?
Is CVE-2026-97688 actively exploited?
What is the CVSS score of CVE-2026-97688?
How do I remediate CVE-2026-97688?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-97688
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