{"id":"CVE-2026-77680","title":"Libsoup3: libsoup: quadratic cpu denial of service in http range coalescing after cve-2025-32907 fix","summary":"An algorithmic complexity flaw exists in libsoup's HTTP Range header processing that persists after the CVE-2025-32907 fix.\n\nCVE-2025-32907 addressed memory amplification when a client repeated the same range many times in a single Range…","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","cvssSource":"cna","cwe":["CWE-407"],"vendor":"Red Hat","product":"libsoup3","affected":["libsoup3 (all versions)"],"ssvc":{"exploitation":"poc","automatable":"yes","technicalImpact":"partial","timestamp":"2026-08-26T12:38:58.296657Z"},"exploitAvailable":true,"published":"2026-08-25","updated":"2026-11-06","sourceUpdated":"2026-11-06T00:45:32.456Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-77680","references":[{"url":"https://access.redhat.com/security/cve/CVE-2025-32907","label":"CVE-2025-32907"},{"url":"https://access.redhat.com/security/cve/CVE-2026-77680"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2520892","label":"RHBZ#2520892"},{"url":"https://gitlab.gnome.org/GNOME/libsoup/-/issues/538"},{"url":"https://gitlab.gnome.org/GNOME/libsoup/-/merge_requests/550"}],"tags":["cve.org","exploit-available"],"epss":0.00344,"epssPercentile":0.28073,"exploits":{"github":1,"githubRepos":["https://github.com/OJ01-creates/CVE-2026-77680-Security-Analysis"],"checkedAt":"2026-11-06T01:43:46.087Z"},"ingestedAt":"2026-11-06T01:43:15.134Z","slug":"CVE-2026-77680","body":"## Overview\n\nAn algorithmic complexity flaw exists in libsoup's HTTP Range header processing that persists after the CVE-2025-32907 fix.\n\nCVE-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.\n\nThe 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.\n\nThis is a CPU exhaustion / availability issue only. No memory corruption or information disclosure occurs.\n\nAffected: libsoup versions containing the CVE-2025-32907 fix but not merge request !550.\nFixed 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.\nUpstream report: https://gitlab.gnome.org/GNOME/libsoup/-/issues/538\nRelated: CVE-2025-32907\n\n## Affected\n\n- `libsoup3 (all versions)`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n### Workarounds\n\nUpgrade to a libsoup version containing merge request !550 (O(N) range coalescing and 200-range limit). Until patched, restrict network access to services using SoupServer, or terminate connections that send Range headers with excessive range counts.","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":29.2,"likelihood":0.1,"exploitation":12,"ransomware":0},"changes":[]}