Vulnerability · Published Aug 25, 2026 · Assigned by redhat
CVE-2026-77680Libsoup3: libsoup: quadratic cpu denial of service in http range coalescing after cve-2025-32907 fix
Medium 5.3
In plain English
A medium-severity security flaw in Red Hat Enterprise Linux 10 from Red Hat. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official description
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
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | libsoup2.4 | no fix listed | DEBIAN-CVE-2026-77680 |
| Debian:13 | libsoup2.4 | no fix listed | DEBIAN-CVE-2026-77680 |
| Debian:12 | libsoup3 | no fix listed | DEBIAN-CVE-2026-77680 |
| Debian:13 | libsoup3 | no fix listed | DEBIAN-CVE-2026-77680 |
| Ubuntu:22.04:LTS | libsoup2.4 | 2.74.2-3ubuntu0.9 | UBUNTU-CVE-2026-77680 |
| Ubuntu:22.04:LTS | libsoup2.4 | 2.74.2-3ubuntu0.9 | USN-8890-1 |
| Ubuntu:24.04:LTS | libsoup2.4 | 2.74.3-6ubuntu1.9 | USN-8890-1 |
| Ubuntu:24.04:LTS | libsoup2.4 | 2.74.3-6ubuntu1.9 | UBUNTU-CVE-2026-77680 |
| Ubuntu:26.10 | libsoup2.4 | no fix listed | UBUNTU-CVE-2026-77680 |
| Ubuntu:24.04:LTS | libsoup3 | 3.4.4-5ubuntu0.9 | UBUNTU-CVE-2026-77680 |
| Ubuntu:24.04:LTS | libsoup3 | 3.4.4-5ubuntu0.9 | USN-8890-1 |
| Ubuntu:26.04:LTS | libsoup3 | 3.6.6-1ubuntu0.1 | UBUNTU-CVE-2026-77680 |
| Ubuntu:26.04:LTS | libsoup3 | 3.6.6-1ubuntu0.1 | USN-8890-1 |
| Ubuntu:26.10 | libsoup3 | 3.6.6-1ubuntu3 | UBUNTU-CVE-2026-77680 |
| Ubuntu:26.10 | libsoup3 | 3.6.6-1ubuntu3 | USN-8890-2 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Red Hat | Red Hat Enterprise Linux 10 | see references |
Weakness: CWE-407 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
References
- CVE-2025-32907 technical-description, x_refsource_REDHAT
- https://access.redhat.com/security/cve/CVE-2026-77680 vdb-entry, x_refsource_REDHAT
- RHBZ#2520892 issue-tracking, x_refsource_REDHAT
- https://gitlab.gnome.org/GNOME/libsoup/-/issues/538
- https://gitlab.gnome.org/GNOME/libsoup/-/merge_requests/550