# CVE-2026-77680: libsoup HTTP Range header algorithmic complexity denial of service

Source: https://junglewise.ai/threats/cve-2026-77680-libsoup-http-range-header-algorithmic-complexity-denial-of  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-25. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-77680 · Severity: medium · CVSS 5.3 · Published 2026-08-25

libsoup is a widely-used HTTP library used in web servers and applications. A flaw in how it processes HTTP Range requests can cause excessive CPU consumption when a client sends a specially-crafted request with thousands of identical range specifications. This can block server processing and cause a denial of service, though no data is exposed or corrupted.

Technologies: [Gnome Libsoup](https://junglewise.ai/threats/technologies/libsoup). Vendors: [Gnome](https://junglewise.ai/threats/vendors/gnome).

## Quick answers

**Is CVE-2026-77680 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77680 being exploited in the wild.

**How severe is CVE-2026-77680?** Medium severity, with a CVSS score of 5.3, published 25 August 2026.

**Which products and versions are affected?** Gnome Libsoup versions containing CVE-2025-32907 fix but prior to MR !550 (before 2026-08-20).

**Is there a fix for CVE-2026-77680?** A patch was published on 2026-08-20: MR !550 merged Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-77680 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-77680?** Check whether you run Gnome Libsoup at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An algorithmic complexity vulnerability exists in libsoup's HTTP Range header coalescing logic in soup_message_headers_get_ranges_internal(). The vulnerable code uses g_array_remove_index() in a loop to coalesce identical ranges, which performs O(N) memmove operations for each removal on the contiguous GArray, resulting in O(N²) overall complexity. The flaw is reachable server-side when a SoupServer handler returns HTTP 200 with a non-empty body. No authentication is required. An attacker can send an HTTP request with up to ~25,000 identical ranges (e.g., bytes=0-0 repeated) within the ~100 KiB header size limit, consuming ~90 ms of single-core CPU per request and blocking the server's event loop. The fix, merged in upstream MR !550 (2026-08-20), replaces per-element removal with O(N) in-place compaction and enforces a 200-range limit per request.

## Affected products

- GNOME libsoup versions containing CVE-2025-32907 fix but prior to MR !550 (before 2026-08-20)

## Timeline

- 2026-08-25: disclosed
- 2026-08-20: patched: MR !550 merged

## Related threats

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- [libsoup heap corruption in WebSocket message reassembly](https://junglewise.ai/threats/cve-2026-102557-a-flaw-was-found-in-libsoup-when-reassembling-fragmented)