CVE-2026-77680 — Libsoup3: libsoup: quadratic cpu denial of service in http range coalescing after cve-2025-32907 fix

Affected: Red Hat Enterprise Linux 10

An algorithmic complexity flaw exists in libsoup's HTTP Range header processing that persists after the CVE-2025-32907 fix.

CVE-2025-32907 addressed memory amplification when a client repeated the same range many times in a single Range header. Commit 9bb92f7a corrected merge correctness in soup_message_headers_get_ranges_internal() in libsoup/soup-message-headers.c, but the coalescing loop still removes merged ranges using g_array_remove_index() for each coalesced element. Because GArray is contiguous, each mid-array removal performs an O(N) memmove. When many identical satisfiable ranges are supplied (for example bytes=0-0 repeated thousands of times), the loop performs O(N²) work coalescing them into a single range.

The vulnerable path is reachable server-side from handle_partial_get() in libsoup/server/http1/soup-server-message-io-http1.c when a SoupServer handler returns HTTP 200 with a non-empty body. No authentication is required. The number of ranges is bounded only by the maximum request header size (~100 KiB), allowing roughly 25,000 ranges per request. Reporter measurements on libsoup HEAD containing the CVE-2025-32907 fix show ~90 ms single-core CPU per such request at the wire maximum, blocking the server's event loop for that duration.

This is a CPU exhaustion / availability issue only. No memory corruption or information disclosure occurs.

Affected: libsoup versions containing the CVE-2025-32907 fix but not merge request !550. Fixed upstream: MR !550 merge…

USN-8890-1 — libsoup2.4, libsoup3 vulnerabilities

Affected: Ubuntu:Pro:16.04:LTS: libsoup2.4, Ubuntu:Pro:18.04:LTS: libsoup2.4, Ubuntu:Pro:20.04:LTS: libsoup2.4, Ubuntu:22.04:LTS: libsoup2.4, Ubuntu:Pro:22.04:LTS: libsoup3, Ubuntu:24.04:LTS: libsoup2.4, Ubuntu:24.04:LTS: libsoup3, Ubuntu:26.04:LTS: libsoup3, Ubuntu:Pro:26.04:LTS: libsoup2.4

It was discovered that libsoup incorrectly handled certain HTTP/2 requests. A remote attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 24.04 LTS and Ubuntu 26.04 LTS. (CVE-2026-4271)

It was discovered that libsoup incorrectly handled certain HTTPS proxy connections. A remote attacker could possibly use this issue to obtain sensitive information. This issue only affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-5119)

It was discovered that libsoup incorrectly parsed certain chunked HTTP requests. A remote attacker could possibly use this issue to bypass security controls. This issue only affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-6324)

It was discovered that libsoup incorrectly handled proxy authentication credentials. A remote attacker could possibly use this issue to obtain sensitive information. (CVE-2026-66339)

It was discovered that libsoup incorrectly handled certain HTTP Range headers. A remote attacker could possibly use this issue to cause a denial of service. (CVE-2026-77014, CVE-2026-77680)

It was discovered that libsoup incorrectly handled certain HTTP/2 connections. A remote attacker could possibly use this issue to obtain sensitive information or execute arbitrary code. This issue only affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-85197)

It was discovered that libsoup incorrectly handled certain HTTP/2 transfers. A…

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CVE-2026-77680 — Libsoup3: libsoup: quadratic cpu denial of service in http range coalescing after cve-2025-32907 fix

USN-8890-1 — libsoup2.4, libsoup3 vulnerabilities