CVE-2026-66338

MEDIUMPre-NVD 5.45.4—
EchelonGraph scoreHIGH confidence

Score 5.4 from GitHub Security Advisory published 2026-07-25. a secondary CVSS source baseline 5.4; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
5.4EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.4Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

A flaw was found in libsoup. The chunked transfer encoding parser uses a permissive parsing function for chunk sizes that silently accepts inputs violating RFC 9112, including leading whitespace, plus sign prefixes, and trailing invalid characters. When libsoup operates behind a strict frontend proxy, this parsing differential can be exploited to smuggle HTTP requests.

CVSS v3
5.4
EG Score
5.4(high)
EG Risk
24(Track)
EG Risk 24/100SSVC: 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
Severity54% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
7%
KEV
Not listed

Published

July 24, 2026

Last Modified

July 27, 2026

Advisory Details (2)

Auto-updated Jul 25, 2026
Patch available. Sources: redhat.
redhat

2506950 – (CVE-2026-66338) CVE-2026-66338 libsoup: libsoup: HTTP Request Smuggling via permissive chunk-size parsing in soup_body_input_stream_read_chunked()

https://bugzilla.redhat.com/show_bug.cgi?id=2506950
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-66338

Vendor Advisories for CVE-2026-66338(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 16× in last 7d / 16× 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.

  1. 2026-07-27 20:43 UTCGHSA enrichment
  2. 2026-07-27 16:26 UTCEG score recompute
  3. 2026-07-27 16:26 UTCGHSA enrichment
  4. 2026-07-27 15:31 UTCEG score recompute
  5. 2026-07-27 15:31 UTCGHSA enrichment
  6. 2026-07-27 14:14 UTCEPSS rescore
  7. 2026-07-27 09:30 UTCEG score recompute
  8. 2026-07-27 09:30 UTCGHSA enrichment
  9. 2026-07-26 14:54 UTCEPSS rescore
  10. 2026-07-26 14:54 UTCEPSS rescore
  11. 2026-07-26 09:43 UTCEG score recompute
  12. 2026-07-26 09:43 UTCGHSA enrichment
  13. 2026-07-25 14:18 UTCEPSS rescore
  14. 2026-07-25 14:18 UTCEPSS rescore
  15. 2026-07-24 23:17 UTCEG score recompute
  16. 2026-07-24 23:16 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-66338?
CVE-2026-66338 is a medium vulnerability published on July 24, 2026. A flaw was found in libsoup. The chunked transfer encoding parser uses a permissive parsing function for chunk sizes that silently accepts inputs violating RFC 9112, including leading whitespace, plus sign prefixes, and trailing invalid characters. When libsoup operates behind a strict frontend…
When was CVE-2026-66338 disclosed?
CVE-2026-66338 was first published in the National Vulnerability Database on July 24, 2026, with the most recent update on July 27, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66338 actively exploited?
CVE-2026-66338 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 92.9% of all scored CVEs.
What is the CVSS score of CVE-2026-66338?
CVE-2026-66338 has a CVSS v3 base score of 5.4 (NVD).
How do I remediate CVE-2026-66338?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66338, 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-2026-66338

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