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).
CSIRTS triage
- What
- There is a remote denial of service vulnerability due to unbounded decompression in websocket permessage-deflate.
- Who is affected
- Deployments of libsoup are affected.
- Urgency
- Remediation is urgent due to the high severity of the vulnerability.
- Action
- Upgrade to a patched version of libsoup.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.55% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 43% of all EPSS-scored CVEs.
Advisory coverage (2)
External references
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