A flaw in libsoup causes a heap buffer overflow when the permessage-deflate WebSocket extension attempts to compress a very large outgoing message. Truncated size calculations used for GByteArray growth can wrap, enabling zlib to write past the allocated buffer. This overflow could permit an attacker to corrupt memory and potentially disrupt service.

Red Hat Enterprise Linux 6, 7, 8, 9 and 10 are affected through the bundled libsoup library. No other vendors are listed.

The CVSS score of 8.6 indicates a high severity flaw. EPSS data is not available and the vulnerability is not listed in the CISA KEV catalog, so no widely known exploits are currently reported. The described heap buffer overflow could lead to memory corruption and service disruption on the server side. The exact conditions required to trigger the overflow are not fully specified, but it happens when the permessage-deflate WebSocket extension compresses a very large outgoing message.