EUVD-2026-66111
GHSA-9m98-w4qj-8f6q
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Network-reachable unauthenticated path with no auth barrier; no confidentiality or integrity impact; availability is limited to event-loop stall rather than complete denial.
Primary rating from Vendor (redhat).
CVSS VectorVendor: redhat
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Lifecycle Timeline
2DescriptionCVE.org
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 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
AnalysisAI
CPU exhaustion in libsoup's HTTP Range header processing affects any SoupServer deployment carrying the CVE-2025-32907 fix but not MR !550. Supplying a Range header with approximately 25,000 repeated satisfiable byte ranges triggers an O(N²) coalescing loop - each g_array_remove_index() call induces an O(N) memmove on GArray - blocking the server's event loop for roughly 90 ms per request from a single unauthenticated client. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires three concurrent conditions: (1) the target application uses libsoup's SoupServer API - libsoup client-only deployments are not in the vulnerable code path; (2) a SoupServer handler returns HTTP 200 with a non-empty body, which is the standard success response pattern and not a special configuration; and (3) the installed libsoup version contains the CVE-2025-32907 fix (commit 9bb92f7a) but not MR !550. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 score of 5.3 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L) correctly characterises a network-reachable, unauthenticated, zero-complexity denial-of-service with limited per-request impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An unauthenticated attacker sends a single HTTP GET request to any endpoint served by a SoupServer instance with a Range header containing approximately 25,000 repetitions of 'bytes=0-0'. The server's handle_partial_get() function invokes the vulnerable O(N²) coalescing loop, consuming roughly 90 ms of CPU on a single core and blocking the event loop for that duration; repeating this at a sustained rate across concurrent connections can render the server unresponsive to legitimate traffic. … |
| Remediation | The upstream fix is GNOME libsoup MR !550, merged 2026-08-20, available at https://gitlab.gnome.org/GNOME/libsoup/-/merge_requests/550; it replaces per-element g_array_remove_index() calls with O(N) in-place compaction and enforces a hard limit of 200 ranges per Range header request. … Detailed patch versions, workarounds, and compensating controls in full report. |
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