CVE-2026-66338

mediumCVSS 5.4covered by 1 sourcefirst seen 2026-07-24

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.

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Exploitation outlook

Low exploitation risk0.17% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 7% of all EPSS-scored CVEs.

Advisory coverage (1)

mediumCVE-2026-66338: A flaw was found in libsoup. The chunked transfer encoding parser uses a permissive parsing fu…nvd · 2026-07-24

External references

NVD record for CVE-2026-66338

CVE.org record

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