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Vulnerabilities

Vulnerability · CVE-2026-85534

Libsoup: libsoup: http/2 client crash in on_data_source_read_callback when settings initial_window_size shrinks during deferred body read

Published Sep 4, 2026 · catalog updated Sep 4, 2026 · Red Hat Red Hat Enterprise Linux 10

Check if you run it

No confirmed exploitation is on record for CVE-2026-85534. EPSS is 0.32%. Act only if a listed version of Red Hat Red Hat Enterprise Linux 10 is installed.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium5.9
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.32%
Remediation
Advisory link
Affected products
vendor Red Hat Red Hat Enterprise Linux 10 · vendor Red Hat Red Hat Enterprise Linux 6 · vendor Red Hat Red Hat Enterprise Linux 7 · vendor Red Hat Red Hat Enterprise Linux 8 · vendor Red Hat Red Hat Enterprise Linux 9

A flaw was found in libsoup. When a client sends an HTTP/2 request body from a non-pollable input stream, the library can buffer more data than the current flow-control window later allows. A malicious HTTP/2 server can shrink SETTINGS_INITIAL_WINDOW_SIZE while that buffered read is still in progress. The client then copies the full buffer into a smaller DATA callback without a runtime bounds check, which can abort the process or fail the HTTP/2 session.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor Red Hat Red Hat Enterprise Linux 10version unspecified
  • vendor Red Hat Red Hat Enterprise Linux 6version unspecified
  • vendor Red Hat Red Hat Enterprise Linux 7version unspecified
  • vendor Red Hat Red Hat Enterprise Linux 8version unspecified
  • vendor Red Hat Red Hat Enterprise Linux 9version unspecified

How to fix CVE-2026-85534

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-85534. EPSS is 0.32%. Act only if a listed version of Red Hat Red Hat Enterprise Linux 10 is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-617. EPSS 0.32%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Ubuntu security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Sep 4, 2026 · CVE.org

    Updated

    A flaw was found in libsoup. When a client sends an HTTP/2 request body from a non-pollable input stream, the library can buffer more data than the current flow-control window later allows. A malicious HTTP/2 server can shrink SETTINGS_INITIAL_WINDOW_SIZE while that buffered read is still in progress. The client then copies the full buffer into a smaller DATA callback without a runtime bounds chec

  2. Oct 21, 2026 · Ubuntu Security Notices

    Detected

    CVE-2026-85534 is listed by USN-8890-2: libsoup vulnerabilities.

Sources

  • CVE.orgVulnerability recordCVE-2026-85534

    A flaw was found in libsoup. When a client sends an HTTP/2 request body from a non-pollable input stream, the library can buffer more data than the current flow-control window later allows. A malicious HTTP/2 server can shrink SETTINGS_INITIAL_WINDOW_SIZE while that buffered read

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-85534

    30-day exploitation probability 0.32%

    first.org
  • Ubuntu Security NoticesVendor advisoryCVE-2026-85534

    USN-8890-1 fixed vulnerabilities in libsoup. This update provides the corresponding updates for libsoup3 on Ubuntu 26.10. Original advisory details: It was discovered that libsoup incorrectly handled certain HTTP/2 requests. A remote attacker could possibly use this issue to caus

    ubuntu.com

References

Freshness

Last verified in this catalog Oct 23, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.