# CVE-2026-102555: Libsoup: libsoup: heap buffer overflow via uninitialized length in data-uri base64 decoding

Status: published. Published: 2026-09-29. Updated: 2026-11-02.

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.

## Remediation

- workaround: To mitigate this do not pass untrusted data URIs to soup_uri_decode_data_uri(). (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 10 (libsoup3): ≥ 0:3.6.5-3.el10_2.20; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 10.0 Extended Update Support (libsoup3): ≥ 0:3.6.5-3.el10_0.19; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (libsoup): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (libsoup): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (libsoup): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (libsoup): Version range not reported. Source: CNA: redhat

## NVD configuration conditions

Affected CPE matches depend on the following AND/OR and negation conditions:

```json
[
  {
    "negate": false,
    "nodes": [
      {
        "cpeMatch": [
          {
            "criteria": "cpe:2.3:a:gnome:libsoup:*:*:*:*:*:*:*:*",
            "versionEndExcluding": "3.7.3",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:redhat:enterprise_linux:9.0:*:*:*:*:*:*:*",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:o:redhat:enterprise_linux:10.0:*:*:*:*:*:*:*",
            "vulnerable": true
          }
        ],
        "negate": false,
        "operator": "OR"
      }
    ],
    "operator": "OR"
  }
]
```

## Severity and prioritization

- CVSS 3.1: 8.2 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H; source: CNA: redhat

- CVSS 3.1: 8.2 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H; source: NVD: secalert@redhat.com

- CISA KEV: No listing in collected sources

- EPSS: 0.37% as of 2026-11-01; percentile 30.78%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-125

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/errata/RHSA-2026:83618 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:93583 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-102555 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2543224 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:83618 (secalert@redhat.com)

- https://access.redhat.com/errata/RHSA-2026:93583 (secalert@redhat.com)

- https://access.redhat.com/security/cve/CVE-2026-102555 (secalert@redhat.com; Mitigation, Vendor Advisory)

- https://bugzilla.redhat.com/show_bug.cgi?id=2543224 (secalert@redhat.com; Issue Tracking, Vendor Advisory)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-102555; retrieved 2026-11-02; source updated 2026-11-02

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-102555; retrieved 2026-11-02; source updated 2026-11-02

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-102555; retrieved 2026-11-02; source updated Not reported

Revision: b213d3c246b060ca4c055f4b150835212bf8dbbac7797df23e772f9473a58c10

Canonical: https://y2.dev/cve/CVE-2026-102555