CVE-2026-53539

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 62% of all CVEs by exploit prediction. 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).

Triggered by: NVD CVSS baseline
Sources: epss, 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

A fix is available — apply it.

Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, when parsing application/x-www-form-urlencoded bodies, QuerystringParser located the field separator with a two step lookup: it first scanned the entire remaining buffer for &, and only when no & existed anywhere ahead did it fall back to scanning for ;. For a body that uses ; as the separator and contains no &, every field iteration performed a full failed & scan over the entire remaining buffer before locating the nearby ;. With N semicolon separated fields in a chunk of size B, this yields O(B^2) byte comparisons per chunk. An attacker can submit a small crafted body of the form a;a;a;... and cause the parser to spend seconds of CPU per request. A handful of concurrent requests can exhaust worker processes. This vulnerability is fixed in 0.0.30.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: 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 computed
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
38%
KEV
Not listed

Published

June 15, 2026

Last Modified

June 26, 2026

Advisory Details (1)

Auto-updated Jun 22, 2026
Patch available. Sources: github.
github Patch Available

Quadratic-time querystring parsing with semicolon separators causes CPU denial of service · Advisory · Kludex/python-multipart · GitHub

https://github.com/Kludex/python-multipart/security/advisories/GHSA-5rvq-cxj2-64vf

Vendor Advisories for CVE-2026-53539(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 / EcosystemFixed in / PatchReleasedSource
redhatjaeger-main-2.19.0-1.hum12026-06-10redhat

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

(5 across 5 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
python-multipart0.0.17-1 ... 0.0.9-1 (14 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
python-multipart0.0.17-1 ... 0.0.9-1 (13 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
python-multipart0.0.20-1, 0.0.20-1.1, 0.0.20-1.1~deb13u1, 0.0.22-1, 0.0.26-1——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
python-multipart0.0.20-1, 0.0.20-1.1, 0.0.20-1.1~deb13u1, 0.0.22-1, 0.0.26-1——
PyPI(1)
PackageVulnerable rangeFixed inDependents
python-multipart0.0.1 ... 0.0.9 (29 versions)0.0.30—

Weakness Classification(2)

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 10× in last 7d / 51× 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.

Showing the most recent 100 of 104 total refreshes for this CVE.

  1. 2026-08-25 13:49 UTCEPSS rescore
  2. 2026-08-24 23:32 UTCEG score recompute
  3. 2026-08-23 09:44 UTCEG score recompute
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  43. 2026-07-15 15:46 UTCVendor advisory
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Frequently asked(5)

What is CVE-2026-53539?
CVE-2026-53539 is a high vulnerability published on June 15, 2026. Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, when parsing application/x-www-form-urlencoded bodies, QuerystringParser located the field separator with a two step lookup: it first scanned the entire remaining buffer for &, and only when no & existed anywhere ahead…
When was CVE-2026-53539 disclosed?
CVE-2026-53539 was first published in the National Vulnerability Database on June 15, 2026, with the most recent update on June 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-53539 actively exploited?
CVE-2026-53539 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 62.1% of all scored CVEs.
What is the CVSS score of CVE-2026-53539?
CVE-2026-53539 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-53539?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-53539, 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

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