Vulnerability Details CVE-2026-66338
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.002
EPSS Ranking 8.7%
CVSS Severity
CVSS v3 Score 5.4
References
Products affected by CVE-2026-66338
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cpe:2.3:a:gnome:libsoup:-
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cpe:2.3:o:redhat:enterprise_linux:10.0
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cpe:2.3:o:redhat:enterprise_linux:6.0
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cpe:2.3:o:redhat:enterprise_linux:7.0
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cpe:2.3:o:redhat:enterprise_linux:8.0
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cpe:2.3:o:redhat:enterprise_linux:9.0