CVE-2026-66338

libsoup: A flaw was found in libsoup

CVE-2026-66338 is fixed in 10 products on 1 platform, first by ALAS2023-2026-3212, released November 7, 2026. It is not reported as exploited. Patch Radar priority: High.

High
CVSS
n/a
important
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0029
21st percentile

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.

Where it's fixed

ProductFixed inFixReleased
Linux
libsoup · amzn 2023 2.72.0-6.amzn2023.0.16 ALAS2023-2026-3212 Nov 7, 2026
libsoup-debuginfo · amzn 2023 2.72.0-6.amzn2023.0.16 ALAS2023-2026-3212 Nov 7, 2026
libsoup-debugsource · amzn 2023 2.72.0-6.amzn2023.0.16 ALAS2023-2026-3212 Nov 7, 2026
libsoup-devel · amzn 2023 2.72.0-6.amzn2023.0.16 ALAS2023-2026-3212 Nov 7, 2026
libsoup-doc · amzn 2023 2.72.0-6.amzn2023.0.16 ALAS2023-2026-3212 Nov 7, 2026
libsoup3 · amzn 2023 3.7.3-1.amzn2023 ALAS2023-2026-3240 Nov 7, 2026
libsoup3-debuginfo · amzn 2023 3.7.3-1.amzn2023 ALAS2023-2026-3240 Nov 7, 2026
libsoup3-debugsource · amzn 2023 3.7.3-1.amzn2023 ALAS2023-2026-3240 Nov 7, 2026
libsoup3-devel · amzn 2023 3.7.3-1.amzn2023 ALAS2023-2026-3240 Nov 7, 2026
libsoup3-doc · amzn 2023 3.7.3-1.amzn2023 ALAS2023-2026-3240 Nov 7, 2026

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