Client process crash via unclamped deferred buffer copy
Published Sep 4, 2026 · Updated Sep 4, 2026
Reachable assertion in libsoup 3.0.0 and later on Red Hat Enterprise Linux 10 allows remote attackers to crash HTTP/2 clients. The non-pollable request-body path buffers an asynchronous read against the old flow-control window, then on_data_source_read_callback copies the full buffer without clamping it to nghttp2's smaller DATA callback length. Exploitation requires an application to upload to an attacker-controlled HTTP/2 server that shrinks SETTINGS_INITIAL_WINDOW_SIZE during the deferred read; Red Hat builds abort rather than corrupt memory.
Summary
What happened
Reachable assertion in libsoup 3.0.0 and later on Red Hat Enterprise Linux 10 allows remote attackers to crash HTTP/2 clients. The non-pollable request-body path buffers an asynchronous read against the old flow-control window, then on_data_source_read_callback copies the full buffer without clamping it to nghttp2's smaller DATA callback length. Exploitation requires an application to upload to an attacker-controlled HTTP/2 server that shrinks SETTINGS_INITIAL_WINDOW_SIZE during the deferred read; Red Hat builds abort rather than corrupt memory.
The record
- CVE
- CVE-2026-85534
- Published
- Sep 4, 2026
- Updated
- Sep 4, 2026
- Vendor
- 389 Directory Server
- Product
- Red Hat Enterprise Linux 10
- Classifications
- CWE-617, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 4, 2026CVE publishedPublication date reported by the CVE source.
- Sep 4, 2026Record updatedLatest update available in the CVE record.
Exploitability
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What is affected?
Published CVSS scores
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Attacks
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Technologies
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Your stack
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