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HIGH

CVE-2026-15709

CVSS v3

7.5

HIGH

EPSS Score

0.9 %

exploit probability, as of 2026-10-18

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • libsoupAlmaLinux:9all versions · fixed in 2.72.0-16.el9_8.3and 1 other package
  • libsoup3AlmaLinux:10all versions · fixed in 3.6.5-3.el10_2.14and 2 other packages

Vendor advisories

  • CVE-2026-15709 Red Hat Product Security240 products fixed · 9 known affected

    SoupWebsocketExtensionDeflate: libsoup: libsoup: WebSocket permessage-deflate Unbounded Decompression Remote Denial of Service

    libsoup as a component of Red Hat Enterprise Linux 6 · libsoup-devel as a component of Red Hat Enterprise Linux 6 · libsoup.src as a component of Red Hat Enterprise Linux 6

  • RHSA-2026:71389 Red Hat Product Security18 products fixed

    Red Hat Security Advisory: libsoup3 security update

  • RHSA-2026:70598 Red Hat Product Security44 products fixed

    Red Hat Security Advisory: libsoup security update

  • RHSA-2026:70599 Red Hat Product Security44 products fixed

    Red Hat Security Advisory: libsoup security update

  • RHSA-2026:69863 Red Hat Product Security32 products fixed

    Red Hat Security Advisory: libsoup security update

  • RHSA-2026:69297 Red Hat Product Security21 products fixed

    Red Hat Security Advisory: libsoup security update

4 more advisories

Full record on NVD

Description

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).

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2026-07-14
Last Modified
2026-07-15

Frequently asked questions

What is CVE-2026-15709?

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).

Is CVE-2026-15709 actively exploited?

Active exploitation of CVE-2026-15709 has not been confirmed. Its EPSS score was 0.9% on 2026-10-18, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-15709?

CVE-2026-15709 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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