# CVE-2026-15709: Soupwebsocketextensiondeflate: libsoup: libsoup: websocket permessage-deflate unbounded decompression remote denial of service Status: published. Published: 2026-07-14. Updated: 2026-11-05. A flaw was found in libsoup's WebSocket implementation when using the permessage-deflate extension. The extension's decompression loop (inflate()) processes data in chunks without enforcing an upper boundary limit on the output buffer size. While libsoup limits the incoming compressed frame size via max_incoming_payload_size, it fails to track or limit memory allocation during decompression. A separate check for decompressed size (max_total_message_size) exists but executes only after inflation is complete, and it is entirely disabled by default for client connections. A remote, unauthenticated attacker can exploit this by sending a small, highly compressed payload (a decompression bomb), causing unbounded memory allocation that triggers an Out-of-Memory (OOM) crash and a Denial of Service (DoS). ## Remediation - workaround: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. (source: CNA: redhat) ## Affected products and versions - Red Hat / Red Hat Enterprise Linux 10 (libsoup3): ≥ 0:3.6.5-3.el10_2.14; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 10.0 Extended Update Support (libsoup3): ≥ 0:3.6.5-3.el10_0.17; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support (libsoup): ≥ 0:2.62.3-2.el8_4.10; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On (libsoup): ≥ 0:2.62.3-2.el8_4.10; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support (libsoup): ≥ 0:2.62.3-2.el8_6.10; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On (libsoup): ≥ 0:2.62.3-2.el8_6.10; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.8 Telecommunications Update Service (libsoup): ≥ 0:2.62.3-3.el8_8.11; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions (libsoup): ≥ 0:2.62.3-3.el8_8.11; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 9 (libsoup): ≥ 0:2.72.0-16.el9_8.3; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions (libsoup): ≥ 0:2.72.0-8.el9_2.13; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions (libsoup): ≥ 0:2.72.0-8.el9_4.12; < * (unaffected, rpm). Source: CNA: redhat - Red Hat / Red Hat Enterprise Linux 9.6 Extended Update Support (libsoup): ≥ 0:2.72.0-10.el9_6.9; < * (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 ## Severity and prioritization - CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: redhat - CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: secalert@redhat.com - CISA KEV: No listing in collected sources - EPSS: 0.88% as of 2026-11-05; percentile 59.32% - SSVC: exploitation poc; automatable yes; technical impact partial; source ADP: CISA-ADP - Weaknesses: CWE-409 ## Exploit evidence - exploit: https://gitlab.gnome.org/GNOME/libsoup/-/issues/511 (ADP: CISA-ADP) ## References - https://access.redhat.com/errata/RHSA-2026:68234 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2026:68235 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2026:68612 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2026:69108 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2026:69297 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2026:69863 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2026:70598 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2026:70599 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/errata/RHSA-2026:71389 (CNA: redhat; vendor-advisory, x_refsource_REDHAT) - https://access.redhat.com/security/cve/CVE-2026-15709 (CNA: redhat; vdb-entry, x_refsource_REDHAT) - https://bugzilla.redhat.com/show_bug.cgi?id=2499922 (CNA: redhat; issue-tracking, x_refsource_REDHAT) - https://gitlab.gnome.org/GNOME/libsoup/-/issues/511 (CNA: redhat) - https://gitlab.gnome.org/GNOME/libsoup/-/issues/511 (ADP: CISA-ADP; exploit) - https://access.redhat.com/errata/RHSA-2026:68234 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2026:68235 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2026:68612 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2026:69108 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2026:69297 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2026:69863 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2026:70598 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2026:70599 (secalert@redhat.com) - https://access.redhat.com/errata/RHSA-2026:71389 (secalert@redhat.com) - https://access.redhat.com/security/cve/CVE-2026-15709 (secalert@redhat.com) - https://bugzilla.redhat.com/show_bug.cgi?id=2499922 (secalert@redhat.com) - https://gitlab.gnome.org/GNOME/libsoup/-/issues/511 (secalert@redhat.com) - https://gitlab.gnome.org/GNOME/libsoup/-/issues/511 (134c704f-9b21-4f2e-91b3-4a467353bcc0) ## Provenance - CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-15709; retrieved 2026-11-05; source updated 2026-11-05 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-15709; retrieved 2026-11-05; source updated 2026-11-05 - FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-15709; retrieved 2026-11-05; source updated Not reported Revision: 58b0522a31f5a78f72c6d5e666e24ed61bea5516d5600202bee0617038ca2f52 Canonical: https://y2.dev/cve/CVE-2026-15709 ## Agent and API access Public CVE pages, Markdown, and JSON are free to read without an account or API key. - Public catalog: https://y2.dev/cve/index.json. 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