CVE 2026 102560

A flaw was found in libsoup. When the permessage-deflate WebSocket extension compresses a very large outgoing message, truncated size calculations used for GByteArray growth could wrap, causing zlib to write past the allocated buffer and resulting in a heap buffer overflow.

This issue is rated Important. Exploitation requires the permessage-deflate extension to be negotiated and a very large outgoing message to be compressed. Applications that enable WebSocket deflate with untrusted or unbounded message sizes are affected. Impact is heap corruption or denial of service.

To mitigate this disable the permessage-deflate WebSocket extension if it is not required, and cap outgoing message sizes.

Bugzilla 2543296 : libsoup: libsoup: Heap buffer overflow during outgoing permessage-deflate buffer growth

CWE-125 : Out-of-bounds Read

Common Vulnerability Scoring System (CVSS) Score Details

Info alert: Important note

CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications ).

The following CVSS metrics and score provided are preliminary and subject to review.

CVSS v3 Score Breakdown

Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

Understanding the Weakness (CWE)

Technical Impact: Read Memory

An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.

Technical Impact: Bypass Protection Mechanism

Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.

Technical Impact: DoS: Crash, Exit, or Restart

An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string.

Technical Impact: Varies by Context

The read operation could produce other undefined or unexpected results.

Red Hat would like to thank Hongduo Zhao for reporting this issue.

Frequently Asked Questions

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Upgrade to a supported product version that includes a fix for this vulnerability (recommended).

Apply a mitigation (if one exists).

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Apply a mitigation (if one exists).

Red Hat Engineering focuses on addressing high-priority issues based on the impact and product lifecycle expectations. Therefore, lower-priority issues will not receive immediate fixes.

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