Libsoup: libsoup: heap buffer overflow via uninitialized length in data-uri base64 decoding (CVE-2026-102555) | HOL Guard CVE

High · CVSS 8.2CVE-2026-102555

Libsoup: libsoup: heap buffer overflow via uninitialized length in data-uri base64 decoding

Answer in brief

CVE-2026-102555 records a High severity (CVSS 8.2) vulnerability in Libsoup: libsoup: heap buffer overflow via uninitialized length in data-uri base64 decoding. The current sources do not mark it as known exploited. The current feed maps Red Hat/libsoup (generic), Red Hat/libsoup3 (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 29, 2026Updated Sep 29, 2026Source checked Sep 29, 2026First seen by HOL Sep 29, 2026Material review Sep 29, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.2
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Not reported

Why this deserves its current priority

CVSS is 8.2. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Red Hat/libsoup (generic), Red Hat/libsoup3 (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Red Hat/libsoupgeneric	*	Not reported
Red Hat/libsoup3generic	*	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Red Hat/libsoup, Red Hat/libsoup3.
Review the reported fix. Source-reported workaround: To mitigate this do not pass untrusted data URIs to soup_uri_decode_data_uri().

Evidence timeline and material changes

Published upstream
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 29, 2026

Sources and claim methodology

Upstream source description

A flaw was found in libsoup. The soup_uri_decode_data_uri() function incorrectly treated base64 data-URI payloads as NUL-terminated strings when calling g_base64_decode_inplace(). If the percent-decoded payload contained embedded NUL bytes, the decoded length could remain uninitialized and be used as the size of the returned GBytes. This can lead to an out-of-bounds read or application crash when processing a crafted data URI.

Quoted source text, attributed separately from HOL analysis.