An algorithmic complexity flaw exists in libsoups 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 servers 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 merged 2026-08-20, replacing per-element removal with O(N) in-place compaction and rejecting Range headers requesting more than 200 ranges. Upstream report: https://gitlab.gnome.org/GNOME/libsoup/-/issues/538 Related: CVE-2025-32907
Weakness
An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Libsoup2.4 | Ubuntu | devel | * |
| Libsoup2.4 | Ubuntu | esm-apps/resolute | * |
| Libsoup2.4 | Ubuntu | esm-infra-legacy/xenial | * |
| Libsoup2.4 | Ubuntu | esm-infra/bionic | * |
| Libsoup2.4 | Ubuntu | esm-infra/focal | * |
| Libsoup2.4 | Ubuntu | jammy | * |
| Libsoup2.4 | Ubuntu | noble | * |
| Libsoup2.4 | Ubuntu | resolute | * |
| Libsoup3 | Ubuntu | devel | * |
| Libsoup3 | Ubuntu | esm-apps/jammy | * |
| Libsoup3 | Ubuntu | jammy | * |
| Libsoup3 | Ubuntu | noble | * |
| Libsoup3 | Ubuntu | resolute | * |
References
- https://access.redhat.com/security/cve/CVE-2025-32907
- https://access.redhat.com/security/cve/CVE-2026-77680
- https://bugzilla.redhat.com/show_bug.cgi?id=2520892
- https://gitlab.gnome.org/GNOME/libsoup/-/issues/538
- https://gitlab.gnome.org/GNOME/libsoup/-/merge_requests/550
- https://gitlab.gnome.org/GNOME/libsoup/-/issues/538